Merge branch 's-draw' into s-gray

Also move the boundary table comment back above its test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -286,7 +286,7 @@ jobs:
           fi
           echo "version=$version" >> "$GITHUB_OUTPUT"
       - name: Run prek
-        uses: j178/prek-action@1382ad72dea72f9d53832f2bcb65b3e87a947204 # v3.0.1
+        uses: j178/prek-action@af4d4fcb6922b8e6f65c0426947125fcc38794ce # v3.0.2
         with:
           prek-version: ${{ steps.prek.outputs.version }}
           # This job only runs on pull requests, so nothing ever populates

esphome/components/mqtt/mqtt_cover.cpp

@@ -50,6 +50,10 @@ void MQTTCoverComponent::setup() {
   }
   if (traits.get_supports_tilt()) {
     this->subscribe(this->get_tilt_command_topic(), [this](const std::string &topic, const std::string &payload) {
+      if (ESPHOME_strcasecmp_P(payload.c_str(), ESPHOME_PSTR("STOP")) == 0) {
+        this->cover_->make_call().set_command_stop_tilt().perform();
+        return;
+      }
       auto value = parse_number<float>(payload);
       if (!value.has_value()) {
         ESP_LOGW(TAG, "Invalid tilt value: '%s'", payload.c_str());

esphome/components/online_image/download_buffer.cpp

@@ -1,5 +1,6 @@
 #include "download_buffer.h"
 #include "esphome/core/log.h"
+#include <algorithm>
 #include <cstring>
 
 namespace esphome::online_image {
@@ -34,6 +35,46 @@ size_t DownloadBuffer::read(size_t len) {
   return this->unread_;
 }
 
+void DownloadSource::compact() {
+  if (this->keep_read_ || this->pos_ == this->start_)
+    return;
+  this->buffer_.read(this->pos_ - this->start_);
+  this->start_ = this->pos_;
+}
+
+int32_t DownloadSource::read(uint8_t *buf, uint32_t len) {
+  const size_t offset = this->pos_ - this->start_;
+  const size_t n = std::min<size_t>(len, this->buffer_.unread() - offset);
+  memcpy(buf, this->buffer_.data(offset), n);
+  this->pos_ += n;
+  return static_cast<int32_t>(n);
+}
+
+bool DownloadSource::seek(uint32_t position) {
+  // Only what is still in the buffer can be read again; a decoder never skips ahead of the download
+  if (position < this->start_ || position > this->start_ + this->buffer_.unread())
+    return false;
+  this->pos_ = position;
+  return true;
+}
+
+bool DownloadBuffer::grow(size_t size) {
+  if (this->size_ >= size)
+    return true;
+  RAMAllocator<uint8_t> allocator;
+  uint8_t *buffer = allocator.allocate(size);
+  if (buffer == nullptr) {
+    ESP_LOGE(TAG, "allocation of %zu bytes failed. Biggest block in heap: %zu Bytes", size,
+             allocator.get_max_free_block_size());
+    return false;
+  }
+  memcpy(buffer, this->buffer_, this->unread_);
+  allocator.deallocate(this->buffer_, this->size_);
+  this->buffer_ = buffer;
+  this->size_ = size;
+  return true;
+}
+
 size_t DownloadBuffer::resize(size_t size) {
   if (this->size_ >= size) {
     // Avoid useless reallocations; if the buffer is big enough, don't reallocate.

esphome/components/online_image/download_buffer.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "esphome/components/runtime_image/image_decoder.h"
 #include "esphome/core/helpers.h"
 #include <cstddef>
 #include <cstdint>
@@ -35,6 +36,8 @@ class DownloadBuffer {
 
   void reset() { this->unread_ = 0; }
   size_t resize(size_t size);
+  /// Make the buffer at least size bytes, keeping the unread data. Returns false if the allocation failed.
+  bool grow(size_t size);
 
  protected:
   uint8_t *buffer_;
@@ -43,4 +46,35 @@ class DownloadBuffer {
   size_t unread_;
 };
 
+/**
+ * @brief Lets a decoder read a download as it arrives, from the download buffer.
+ *
+ * The decoder reads at its own position in the buffer. Bytes it has read stay there until compact() drops
+ * them, and compact() keeps everything while set_keep_read(true) is in effect, so the decoder can seek back
+ * while it reads the headers.
+ */
+class DownloadSource : public runtime_image::DecodeSource {
+ public:
+  explicit DownloadSource(DownloadBuffer &buffer) : buffer_(buffer) {}
+
+  /// Start again at the beginning of a new download, keeping what is read
+  void reset() {
+    this->start_ = 0;
+    this->pos_ = 0;
+    this->keep_read_ = true;
+  }
+  void set_keep_read(bool keep) { this->keep_read_ = keep; }
+  /// Drop the bytes the decoder has read, to make room for more of the download
+  void compact();
+
+  int32_t read(uint8_t *buf, uint32_t len) override;
+  bool seek(uint32_t position) override;
+
+ protected:
+  DownloadBuffer &buffer_;
+  size_t start_{0};  // Position in the download of the first byte in the buffer
+  size_t pos_{0};    // Position in the download the decoder reads next
+  bool keep_read_{true};
+};
+
 }  // namespace esphome::online_image

esphome/components/online_image/image.py

@@ -22,6 +22,8 @@ DEPENDENCIES = ["http_request"]
 CODEOWNERS = ["@guillempages", "@clydebarrow"]
 
 CONF_ON_DOWNLOAD_FINISHED = "on_download_finished"
+CONF_ON_DOWNLOAD_STARTED = "on_download_started"
+CONF_ON_DOWNLOAD_PROGRESS = "on_download_progress"
 CONF_UPDATE = "update"
 
 online_image_ns = cg.esphome_ns.namespace("online_image")
@@ -43,7 +45,9 @@ ONLINE_IMAGE_SCHEMA = (
             cv.Optional(CONF_REQUEST_HEADERS): cv.All(
                 cv.Schema({cv.string: cv.templatable(cv.string)})
             ),
+            cv.Optional(CONF_ON_DOWNLOAD_STARTED): automation.validate_automation({}),
             cv.Optional(CONF_ON_DOWNLOAD_FINISHED): automation.validate_automation({}),
+            cv.Optional(CONF_ON_DOWNLOAD_PROGRESS): automation.validate_automation({}),
             cv.Optional(CONF_ON_ERROR): automation.validate_automation({}),
         }
     )
@@ -96,9 +100,17 @@ automation.register_apply_action(
 
 
 _CALLBACK_AUTOMATIONS = (
+    automation.CallbackAutomation(
+        CONF_ON_DOWNLOAD_STARTED, "add_on_download_started_callback"
+    ),
     automation.CallbackAutomation(
         CONF_ON_DOWNLOAD_FINISHED, "add_on_finished_callback", [(bool, "cached")]
     ),
+    automation.CallbackAutomation(
+        CONF_ON_DOWNLOAD_PROGRESS,
+        "add_on_progress_callback",
+        [(float, "progress"), (cg.size_t, "bytes_read")],
+    ),
     automation.CallbackAutomation(CONF_ON_ERROR, "add_on_error_callback"),
 )
 

esphome/components/online_image/online_image.cpp

@@ -4,6 +4,7 @@
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include <algorithm>
+#include <cmath>
 #include <cstdio>
 
 ESPHOME_LOG_TAG(TAG, "online_image");
@@ -15,6 +16,11 @@ static const char *const IF_MODIFIED_SINCE_HEADER_NAME = "if-modified-since";
 
 namespace esphome::online_image {
 
+// Time one loop pass may spend reading, and decoding a JPEG as it downloads
+static constexpr uint32_t PASS_BUDGET_MS = 20;
+// Shortest time between two on_download_progress calls
+static constexpr uint32_t PROGRESS_INTERVAL_MS = 100;
+
 OnlineImage::OnlineImage(const std::string &url, int width, int height, runtime_image::ImageFormat format,
                          image::ImageType type, image::Transparency transparency, image::Image *placeholder,
                          uint32_t buffer_size, bool is_big_endian)
@@ -140,8 +146,12 @@ void OnlineImage::update() {
     return;
   }
 
-  // JPEG requires the complete image in the download buffer before decoding
-  if (format == runtime_image::JPEG && total_size > this->download_buffer_.size() &&
+  // A JPEG of known size is decoded as it arrives, so the download buffer only has to hold its headers.
+  // Otherwise the decoder needs the complete image in the buffer.
+  this->streaming_ = total_size > 0 && total_size <= INT32_MAX && this->decoder_supports_source();
+  this->stream_started_ = false;
+  this->source_.reset();
+  if (!this->streaming_ && format == runtime_image::JPEG && total_size > this->download_buffer_.size() &&
       this->download_buffer_.resize(total_size) == 0) {
     // resize() logged the failed allocation; the next update() allocates the configured buffer again
     this->end_connection_();
@@ -152,6 +162,8 @@ void OnlineImage::update() {
   ESP_LOGI(TAG, "Downloading image (Size: %zu)", total_size);
   this->start_time_ = millis();
   this->last_data_time_ = this->start_time_;
+  this->download_started_callback_.call();
+  this->report_progress_(true);
   this->enable_loop();
 }
 
@@ -169,6 +181,11 @@ void OnlineImage::loop() {
     return;
   }
 
+  if (this->streaming_) {
+    this->loop_stream_();
+    return;
+  }
+
   // Check if download is complete — use decoder's format-specific completion check
   // to handle both known content-length and chunked transfer encoding
   if (this->is_decode_finished() || (this->downloader_->content_length > 0 &&
@@ -179,15 +196,22 @@ void OnlineImage::loop() {
   }
 
   // Download and decode more data
-  size_t available = this->download_buffer_.free_capacity();
-  if (available > 0) {
-    // Download in chunks to avoid blocking
-    available = std::min(available, this->download_buffer_initial_size_);
-    auto len = this->downloader_->read(this->download_buffer_.append(), available);
-
-    if (len > 0) {
-      this->last_data_time_ = App.get_loop_component_start_time();
+  if (this->download_buffer_.free_capacity() > 0) {
+    const uint32_t now = App.get_loop_component_start_time();
+    size_t received = 0;
+    int len;
+    do {
+      len = this->downloader_->read(this->download_buffer_.append(),
+                                    std::min(this->download_buffer_.free_capacity(), READ_CHUNK));
+      if (len <= 0)
+        break;
       this->download_buffer_.write(len);
+      received += len;
+    } while (this->download_buffer_.free_capacity() != 0 && millis() - now < PASS_BUDGET_MS);
+
+    if (received > 0) {
+      this->last_data_time_ = now;
+      this->report_progress_(false);
 
       // Feed data to decoder
       auto consumed = this->feed_data(this->download_buffer_.data(), this->download_buffer_.unread());
@@ -255,6 +279,114 @@ void OnlineImage::loop() {
   }
 }
 
+void OnlineImage::loop_stream_() {
+  const uint32_t now = App.get_loop_component_start_time();
+  const size_t total = this->downloader_->content_length;
+  if (this->stream_started_)
+    this->source_.compact();
+
+  if (this->downloader_->get_bytes_read() < total) {
+    if (this->download_buffer_.free_capacity() == 0) {
+      // compact() already ran, so a full buffer means the decoder read nothing in the last pass
+      if (now - this->last_data_time_ >= this->parent_->get_timeout()) {
+        ESP_LOGE(TAG, "Image does not fit in the %zu byte download buffer; increase buffer_size",
+                 this->download_buffer_.size());
+        this->fail_download_();
+        return;
+      }
+    } else {
+      int len;
+      do {
+        len = this->downloader_->read(this->download_buffer_.append(),
+                                      std::min(this->download_buffer_.free_capacity(), READ_CHUNK));
+        if (len <= 0)
+          break;
+        this->last_data_time_ = now;
+        this->download_buffer_.write(len);
+        this->report_progress_(false);
+      } while (this->downloader_->get_bytes_read() < total && this->download_buffer_.free_capacity() != 0 &&
+               millis() - now < PASS_BUDGET_MS);
+      if (len < 0) {
+        ESP_LOGE(TAG, "Error downloading image: %d", len);
+        this->fail_download_();
+        return;
+      } else if (now - this->last_data_time_ >= this->parent_->get_timeout()) {
+        ESP_LOGE(TAG, "No data received for %" PRIu32 " ms", this->parent_->get_timeout());
+        this->fail_download_();
+        return;
+      }
+    }
+  }
+  const bool arrived = this->downloader_->get_bytes_read() >= total;
+
+  if (!this->stream_started_) {
+    // The decoder reads the headers when it opens the image, so wait until they are in the buffer
+    if (!arrived && this->download_buffer_.free_capacity() != 0)
+      return;
+    const int err = this->begin_source(&this->source_);
+    if (err != 0) {
+      // Headers cut short by a full buffer fail to parse, or make the decoder seek past the buffer. Such an image
+      // still decodes once it is all in memory, as it did before JPEG images were decoded as they download.
+      if (!arrived && (err == runtime_image::DECODE_ERROR_INVALID_TYPE || err == runtime_image::DECODE_ERROR_READ)) {
+        ESP_LOGW(TAG,
+                 "The image headers do not fit the %zu byte download buffer, so the whole image is downloaded "
+                 "before it is decoded; increase buffer_size to decode it as it downloads",
+                 this->download_buffer_.size());
+        // grow() logs a failed allocation
+        if (this->download_buffer_.grow(total)) {
+          this->streaming_ = false;
+        } else {
+          this->fail_download_();
+        }
+        return;
+      }
+      ESP_LOGE(TAG, "Error decoding image: %s", runtime_image::decode_error_to_string(err));
+      this->fail_download_();
+      return;
+    }
+    this->source_.set_keep_read(false);
+    this->stream_started_ = true;
+    // Opening the image and allocating its buffer is enough for one pass
+    return;
+  }
+
+  do {
+    const int result = this->decode_step();
+    if (result == runtime_image::DECODE_STEP_MORE)
+      continue;
+    if (result == runtime_image::DECODE_STEP_DONE) {
+      this->finish_download_();
+    } else if (result == runtime_image::DECODE_STEP_NEED_DATA) {
+      if (!arrived)
+        return;
+      // JPEGDEC only waits for bytes short of the size it was given, so this guards against a hang
+      ESP_LOGE(TAG, "Download ended before the image was complete");
+      this->fail_download_();
+    } else {
+      ESP_LOGE(TAG, "Error decoding image: %s", runtime_image::decode_error_to_string(result));
+      this->fail_download_();
+    }
+    return;
+  } while (millis() - now < PASS_BUDGET_MS);
+}
+
+void OnlineImage::report_progress_(bool force) {
+  const uint32_t now = App.get_loop_component_start_time();
+  const size_t bytes = this->downloader_->get_bytes_read();
+  const size_t total = this->downloader_->content_length;
+  // The last bytes are always reported, so a progress bar reaches 100%
+  if (!force && now - this->last_progress_time_ < PROGRESS_INTERVAL_MS && (total == 0 || bytes < total))
+    return;
+  this->last_progress_time_ = now;
+  const float progress = total > 0 ? std::min(100.0f, bytes * 100.0f / total) : NAN;
+  this->download_progress_callback_.call(progress, bytes);
+}
+
+void OnlineImage::fail_download_() {
+  this->end_connection_();
+  this->download_error_callback_.call();
+}
+
 void OnlineImage::finish_download_() {
   // Must be read before end_decode() ends the decoding session
   bool decoder_finished = this->is_decode_finished();
@@ -288,6 +420,8 @@ void OnlineImage::end_connection_() {
     this->downloader_ = nullptr;
   }
   this->download_buffer_.reset();
+  this->streaming_ = false;
+  this->stream_started_ = false;
   this->disable_loop();
 }
 

esphome/components/online_image/online_image.h

@@ -16,6 +16,10 @@ using t_http_codes = enum {
   HTTP_CODE_NOT_FOUND = 404,
 };
 
+/// Largest download read(). A read() blocks until it has every byte it asked for, so this bounds how long one loop
+/// pass waits on a slow link.
+static constexpr size_t READ_CHUNK = 1460;
+
 /**
  * @brief Download an image from a given URL, and decode it using the specified decoder.
  * The image will then be stored in a buffer, so that it can be re-displayed without the
@@ -70,9 +74,17 @@ class OnlineImage final : public PollingComponent,
    */
   void release();
 
+  /// Called when the server has accepted the request and the image starts to download
+  template<typename F> void add_on_download_started_callback(F &&callback) {
+    this->download_started_callback_.add(std::forward<F>(callback));
+  }
   template<typename F> void add_on_finished_callback(F &&callback) {
     this->download_finished_callback_.add(std::forward<F>(callback));
   }
+  /// Called with the percentage downloaded (NAN when the server did not send the size) and the bytes read so far
+  template<typename F> void add_on_progress_callback(F &&callback) {
+    this->download_progress_callback_.add(std::forward<F>(callback));
+  }
   template<typename F> void add_on_error_callback(F &&callback) {
     this->download_error_callback_.add(std::forward<F>(callback));
   }
@@ -81,12 +93,20 @@ class OnlineImage final : public PollingComponent,
   bool validate_url_(const std::string &url);
   void end_connection_();
   void finish_download_();
+  /// loop() for a JPEG that is decoded as it downloads
+  void loop_stream_();
+  void fail_download_();
+  /// Reports download progress, at most every PROGRESS_INTERVAL_MS unless force is set
+  void report_progress_(bool force);
 
   CallbackManager<void(bool)> download_finished_callback_{};
   CallbackManager<void()> download_error_callback_{};
+  LazyCallbackManager<void()> download_started_callback_{};
+  LazyCallbackManager<void(float, size_t)> download_progress_callback_{};
 
   std::shared_ptr<http_request::HttpContainer> downloader_{nullptr};
   DownloadBuffer download_buffer_;
+  DownloadSource source_{download_buffer_};
   /**
    * This is the *initial* size of the download buffer, not the current size.
    * The download buffer can be resized at runtime; the download_buffer_initial_size_
@@ -109,6 +129,9 @@ class OnlineImage final : public PollingComponent,
 
   uint32_t start_time_{0};
   uint32_t last_data_time_{0};
+  uint32_t last_progress_time_{0};
+  bool streaming_{false};       // The decoder reads the download itself, as it arrives
+  bool stream_started_{false};  // The decoder has read the headers
 };
 
 }  // namespace esphome::online_image

esphome/components/runtime_image/__init__.py

@@ -92,7 +92,17 @@ class JPEGFormat(Format):
 
     def actions(self) -> None:
         cg.add_define("USE_RUNTIME_IMAGE_JPEG")
-        cg.add_library("JPEGDEC", "1.8.4", "https://github.com/bitbank2/JPEGDEC#1.8.4")
+        # 1.8.4 plus decodeBegin()/decodeRows(), so an image can be decoded a few rows at a time and
+        # can wait for input that has not arrived yet, and fixes for: input that arrives in short
+        # reads, garbled RGB8888 output of grayscale images, and two ARM NEON faults seen on arm64 hosts
+        # (swapped red and blue in the 4:2:0 RGB8888 path, writes past the row on clipped MCUs). It also
+        # uses the ESP32-S3 SIMD colour conversion in ESP-IDF builds, not only Arduino ones, and is built
+        # with -O2.
+        cg.add_library(
+            "JPEGDEC",
+            "1.8.4",
+            "https://github.com/esphome-libs/JPEGDEC#1.8.4-esphome.3",
+        )
         if CORE.is_host:
             # JPEGDEC's host detection checks __MACH__/__LINUX__, but gcc only
             # predefines the lowercase __linux__; without this a Linux host

esphome/components/runtime_image/image_decoder.cpp

@@ -2,7 +2,6 @@
 #include "runtime_image.h"
 #include "esphome/core/log.h"
 #include <algorithm>
-#include <cmath>
 
 namespace esphome::runtime_image {
 
@@ -11,19 +10,48 @@ ESPHOME_LOG_TAG(TAG, "image_decoder");
 bool ImageDecoder::set_size(int width, int height) {
   bool success = this->image_->resize(width, height) > 0;
   this->size_valid_ = success;
-  this->x_scale_ = static_cast<double>(this->image_->get_buffer_width()) / width;
-  this->y_scale_ = static_cast<double>(this->image_->get_buffer_height()) / height;
+  this->draw_width_ = width;
+  this->draw_height_ = height;
   return success;
 }
 
+int ImageDecoder::scaled_x_(int x) const {
+  if (this->draw_width_ <= 0)
+    return 0;
+  const uint32_t buffer_width = this->image_->get_buffer_width();
+  return static_cast<int>((static_cast<uint32_t>(x) * buffer_width + this->draw_width_ - 1) / this->draw_width_);
+}
+
+int ImageDecoder::scaled_y_(int y) const {
+  if (this->draw_height_ <= 0)
+    return 0;
+  const uint32_t buffer_height = this->image_->get_buffer_height();
+  return static_cast<int>((static_cast<uint32_t>(y) * buffer_height + this->draw_height_ - 1) / this->draw_height_);
+}
+
 void ImageDecoder::draw(int x, int y, int w, int h, const Color &color) {
   if (!this->size_valid_) {
     return;
   }
-  auto width = std::min(this->image_->get_buffer_width(), static_cast<int>(std::ceil((x + w) * this->x_scale_)));
-  auto height = std::min(this->image_->get_buffer_height(), static_cast<int>(std::ceil((y + h) * this->y_scale_)));
-  for (int i = x * this->x_scale_; i < width; i++) {
-    for (int j = y * this->y_scale_; j < height; j++) {
+  // A source pixel paints the target pixels from ceil(start * scale) up to ceil(end * scale). The spans of neighbouring
+  // pixels meet without overlapping, so when an image is shrunk each target pixel is painted once, by the first
+  // source pixel that reaches it, rather than by every pixel that lands on it. Integer maths: the S3 has no double FPU.
+  const int buffer_width = this->image_->get_buffer_width();
+  const int buffer_height = this->image_->get_buffer_height();
+  int x1 = x;
+  int y1 = y;
+  int x2 = x + w;
+  int y2 = y + h;
+  if (buffer_width != this->draw_width_ || buffer_height != this->draw_height_) {
+    x1 = this->scaled_x_(x);
+    y1 = this->scaled_y_(y);
+    x2 = this->scaled_x_(x + w);
+    y2 = this->scaled_y_(y + h);
+  }
+  x2 = std::min(buffer_width, x2);
+  y2 = std::min(buffer_height, y2);
+  for (int i = x1; i < x2; i++) {
+    for (int j = y1; j < y2; j++) {
       this->image_->draw_pixel(i, j, color);
     }
   }

esphome/components/runtime_image/image_decoder.h

@@ -1,4 +1,6 @@
 #pragma once
+#include <cstdint>
+
 #include "esphome/core/color.h"
 #include "image_format.h"
 
@@ -9,6 +11,14 @@ enum DecodeError : int {
   DECODE_ERROR_UNSUPPORTED_FORMAT = -2,
   DECODE_ERROR_OUT_OF_MEMORY = -3,
   DECODE_ERROR_INTERNAL_DECODER_ERROR = -4,
+  DECODE_ERROR_READ = -5,
+};
+
+/// Results of ImageDecoder::decode_step() other than a DecodeError
+enum DecodeStep : int {
+  DECODE_STEP_DONE = 0,
+  DECODE_STEP_MORE = 1,
+  DECODE_STEP_NEED_DATA = 2,  // The source has nothing more yet; call again once more has arrived
 };
 
 constexpr const char *decode_error_to_string(int error) {
@@ -21,6 +31,8 @@ constexpr const char *decode_error_to_string(int error) {
       return "Out of memory";
     case DECODE_ERROR_INTERNAL_DECODER_ERROR:
       return "Internal decoder error";
+    case DECODE_ERROR_READ:
+      return "Read error";
     default:
       return "Unknown error";
   }
@@ -28,6 +40,19 @@ constexpr const char *decode_error_to_string(int error) {
 
 class RuntimeImage;
 
+/// Input that a decoder reads itself as it goes, so the whole image never has to be in memory at once
+class DecodeSource {
+ public:
+  virtual ~DecodeSource() = default;
+  /**
+   * Read up to len bytes at the current position. Returns the number read, which is less than len, even 0, when
+   * no more has arrived yet or at the end of the input, or negative on error.
+   */
+  virtual int32_t read(uint8_t *buf, uint32_t len) = 0;
+  /// Move to a position counted from the start. Returns false on error.
+  virtual bool seek(uint32_t position) = 0;
+};
+
 /**
  * @brief Class to abstract decoding different image formats.
  */
@@ -58,8 +83,8 @@ class ImageDecoder {
     this->expected_size_ = 0;
     this->decoded_bytes_ = 0;
     this->size_valid_ = true;
-    this->x_scale_ = 1.0;
-    this->y_scale_ = 1.0;
+    this->draw_width_ = 0;
+    this->draw_height_ = 0;
   }
 
   /**
@@ -88,6 +113,28 @@ class ImageDecoder {
    */
   virtual int decode(uint8_t *buffer, size_t size) = 0;
 
+  /// Whether this decoder can read a DecodeSource itself, a step at a time, instead of being fed data.
+  virtual bool supports_source() const { return false; }
+
+  /**
+   * @brief Start decoding from a source the decoder reads itself. Call after prepare(), in place of decode().
+   *
+   * The image headers (everything before the image data) must be readable from the source when this is called;
+   * only decode_step() can wait for more to arrive. The source must hold expected_size bytes in the end, and stay
+   * valid until the session ends.
+   * @return int 0 on success, or a {@see DecodeError} value.
+   */
+  virtual int begin_source(DecodeSource *source) { return DECODE_ERROR_UNSUPPORTED_FORMAT; }
+
+  /**
+   * @brief Decode a little more of an image started with begin_source(), keeping each call short.
+   *
+   * @return int DECODE_STEP_MORE while there is more to do, DECODE_STEP_NEED_DATA when the source has not
+   *             delivered enough to go on, DECODE_STEP_DONE when the image is complete, or a {@see DecodeError}
+   *             value.
+   */
+  virtual int decode_step() { return DECODE_ERROR_UNSUPPORTED_FORMAT; }
+
   /**
    * @brief Request the image to be resized once the actual dimensions are known.
    * Called by the callback functions, to be able to access the parent Image class.
@@ -112,6 +159,9 @@ class ImageDecoder {
    */
   void draw(int x, int y, int w, int h, const Color &color);
 
+  /// Bytes of the image the decoder has used so far
+  size_t get_decoded_bytes() const { return this->decoded_bytes_; }
+
   /**
    * @brief Check if the decoder has finished processing.
    *
@@ -134,8 +184,13 @@ class ImageDecoder {
   uint8_t *image_buffer_() const;
   bool image_is_big_endian_() const;
 
-  double x_scale_ = 1.0;
-  double y_scale_ = 1.0;
+  /// The first buffer column, or row, that source column x, or row y, paints: ceil(x * buffer size / draw size)
+  int scaled_x_(int x) const;
+  int scaled_y_(int y) const;
+
+  // Size of the image as the decoder draws it, which draw() spreads over the buffer
+  int draw_width_ = 0;
+  int draw_height_ = 0;
   RuntimeImage *image_;
   size_t expected_size_ = 0;  // Expected data size (0 if unknown)
   size_t decoded_bytes_ = 0;  // Bytes processed so far

esphome/components/runtime_image/jpeg_decoder.cpp

@@ -31,8 +31,8 @@ bool JpegDecoder::prepare_rgb565_scaling_(int width, int height) {
   const uint32_t target_width = this->image_->get_buffer_width();
   const uint32_t target_height = this->image_->get_buffer_height();
   // Boundary n is the first target pixel source pixel n covers, rounded up. When shrinking, the source
-  // pixel whose span lands on a target pixel paints it, so an 8 to 4 scale keeps columns 0, 2, 4 and 6;
-  // the generic draw() path rounds down and keeps the odd ones instead
+  // pixel whose span lands on a target pixel paints it, so an 8 to 4 scale keeps columns 0, 2, 4 and 6,
+  // as the generic draw() path does
   for (uint32_t x = 0; x <= static_cast<uint32_t>(width); x++) {
     this->x_boundaries_.push_back(static_cast<uint16_t>((x * target_width + width - 1) / width));
   }
@@ -135,13 +135,24 @@ int HOT JpegDecoder::decode(uint8_t *buffer, size_t size) {
     ESP_LOGE(TAG, "Could not open image for decoding: %d", this->jpeg_.getLastError());
     return DECODE_ERROR_INVALID_TYPE;
   }
+  const int err = this->start_();
+  if (err != 0)
+    return err;
+  if (!this->jpeg_.decode(0, 0, this->scale_option_()))
+    return this->fail_();
+  this->decoded_bytes_ = size;
+  this->jpeg_.close();
+  return size;
+}
+
+int JpegDecoder::start_() {
   auto jpeg_type = this->jpeg_.getJPEGType();
   if (jpeg_type == JPEG_MODE_INVALID) {
     ESP_LOGE(TAG, "Unsupported JPEG image");
     return DECODE_ERROR_INVALID_TYPE;
   } else if (jpeg_type == JPEG_MODE_PROGRESSIVE) {
     ESP_LOGE(TAG, "Progressive JPEG images not supported");
-    return DECODE_ERROR_INVALID_TYPE;
+    return DECODE_ERROR_UNSUPPORTED_FORMAT;
   }
   ESP_LOGD(TAG, "Image size: %d x %d, bpp: %d", this->jpeg_.getWidth(), this->jpeg_.getHeight(), this->jpeg_.getBpp());
 
@@ -154,32 +165,133 @@ int HOT JpegDecoder::decode(uint8_t *buffer, size_t size) {
   } else {
     this->jpeg_.setPixelType(RGB8888);
   }
-  if (!this->set_size(this->jpeg_.getWidth(), this->jpeg_.getHeight())) {
+  const int width = this->jpeg_.getWidth();
+  const int height = this->jpeg_.getHeight();
+  if (!this->set_size(width, height)) {
     return DECODE_ERROR_OUT_OF_MEMORY;
   }
-  if (this->direct_rgb565_ && !this->prepare_rgb565_scaling_(this->jpeg_.getWidth(), this->jpeg_.getHeight())) {
+  // JPEGDEC can decode at 1/2, 1/4 or 1/8 size for much less work. Use the smallest size that still has at least as
+  // many pixels as the buffer, so a large image shown small is not decoded in full only to be thrown away.
+  const int buffer_width = this->image_->get_buffer_width();
+  const int buffer_height = this->image_->get_buffer_height();
+  this->scale_ = 1;
+  while (this->scale_ < JPEG_SCALE_EIGHTH && width / (this->scale_ * 2) >= buffer_width &&
+         height / (this->scale_ * 2) >= buffer_height) {
+    this->scale_ *= 2;
+  }
+  const int decoded_width = (width + this->scale_ - 1) / this->scale_;
+  const int decoded_height = (height + this->scale_ - 1) / this->scale_;
+  this->draw_width_ = decoded_width;
+  this->draw_height_ = decoded_height;
+  if (this->scale_ != 1) {
+    ESP_LOGD(TAG, "Decoding at 1/%d size, %d x %d", this->scale_, decoded_width, decoded_height);
+  }
+  if (this->direct_rgb565_ && !this->prepare_rgb565_scaling_(decoded_width, decoded_height)) {
     return DECODE_ERROR_OUT_OF_MEMORY;
   }
-  if (!this->jpeg_.decode(0, 0, 0)) {
-    auto error = this->jpeg_.getLastError();
-    ESP_LOGE(TAG, "Error while decoding: %d", error);
-    this->jpeg_.close();
-    switch (error) {
-      case JPEG_ERROR_MEMORY:
-        return DECODE_ERROR_OUT_OF_MEMORY;
-      case JPEG_UNSUPPORTED_FEATURE:
-        return DECODE_ERROR_UNSUPPORTED_FORMAT;
-      case JPEG_INVALID_FILE:
-      case JPEG_INVALID_PARAMETER:
-        return DECODE_ERROR_INVALID_TYPE;
-      case JPEG_DECODE_ERROR:
-      default:
-        return DECODE_ERROR_INTERNAL_DECODER_ERROR;
-    }
-  }
-  this->decoded_bytes_ = size;
+  return 0;
+}
+
+int JpegDecoder::fail_() {
+  const bool read_failed = this->source_ != nullptr && this->source_failed_;
+  const int error = this->jpeg_.getLastError();
   this->jpeg_.close();
-  return size;
+  this->source_ = nullptr;
+  if (read_failed) {
+    ESP_LOGE(TAG, "Reading the image failed");
+    return DECODE_ERROR_READ;
+  }
+  ESP_LOGE(TAG, "Error while decoding: %d", error);
+  switch (error) {
+    case JPEG_ERROR_MEMORY:
+      return DECODE_ERROR_OUT_OF_MEMORY;
+    case JPEG_UNSUPPORTED_FEATURE:
+      return DECODE_ERROR_UNSUPPORTED_FORMAT;
+    case JPEG_INVALID_FILE:
+    case JPEG_INVALID_PARAMETER:
+      return DECODE_ERROR_INVALID_TYPE;
+    case JPEG_DECODE_ERROR:
+    default:
+      return DECODE_ERROR_INTERNAL_DECODER_ERROR;
+  }
+}
+
+void JpegDecoder::reset() {
+  // A decode from a source that was given up part way still has the image open
+  if (this->source_ != nullptr) {
+    this->jpeg_.close();
+    this->source_ = nullptr;
+  }
+  ImageDecoder::reset();
+}
+
+int32_t JpegDecoder::source_read(JPEGFILE *file, uint8_t *buf, int32_t len) {
+  auto *decoder = static_cast<JpegDecoder *>(file->fHandle);
+  const int32_t n = decoder->source_->read(buf, len);
+  if (n < 0) {
+    // JPEGDEC has no way to report a failed read, so remember it and give it no data
+    decoder->source_failed_ = true;
+    return 0;
+  }
+  file->iPos += n;
+  return n;
+}
+
+int32_t JpegDecoder::source_seek(JPEGFILE *file, int32_t position) {
+  auto *decoder = static_cast<JpegDecoder *>(file->fHandle);
+  if (position < 0 || !decoder->source_->seek(position)) {
+    decoder->source_failed_ = true;
+    return file->iPos;
+  }
+  file->iPos = position;
+  return position;
+}
+
+int JpegDecoder::begin_source(DecodeSource *source) {
+  if (this->expected_size_ == 0 || this->expected_size_ > INT32_MAX) {
+    ESP_LOGE(TAG, "Image size %zu cannot be read from a source", this->expected_size_);
+    return DECODE_ERROR_INVALID_TYPE;
+  }
+  if (!source->seek(0)) {
+    ESP_LOGE(TAG, "Could not read the image");
+    return DECODE_ERROR_READ;
+  }
+  this->source_ = source;
+  this->source_failed_ = false;
+  if (!this->jpeg_.open(this, this->expected_size_, source_close, source_read, source_seek, draw_callback)) {
+    // The caller may recover, for example by reading the whole image first, so it reports the failure
+    ESP_LOGD(TAG, "Could not open image for decoding: %d", this->jpeg_.getLastError());
+    this->source_ = nullptr;
+    return this->source_failed_ ? DECODE_ERROR_READ : DECODE_ERROR_INVALID_TYPE;
+  }
+  const int err = this->start_();
+  if (err != 0) {
+    this->jpeg_.close();
+    this->source_ = nullptr;
+    return err;
+  }
+  if (!this->jpeg_.decodeBegin(0, 0, this->scale_option_()))
+    return this->fail_();
+  return 0;
+}
+
+int HOT JpegDecoder::decode_step() {
+  if (this->source_ == nullptr)
+    return DECODE_ERROR_INVALID_TYPE;
+  const int result = this->jpeg_.decodeRows(1);
+  // JPEGDEC may decode on with the missing data, so check the read before its result
+  if (this->source_failed_)
+    return this->fail_();
+  if (result == JPEG_DECODE_MORE)
+    return DECODE_STEP_MORE;
+  if (result == JPEG_DECODE_NEED_DATA)
+    return DECODE_STEP_NEED_DATA;
+  if (result == 0)
+    return this->fail_();
+  this->decoded_bytes_ = this->expected_size_;
+  this->jpeg_.close();
+  this->source_ = nullptr;
+  return DECODE_STEP_DONE;
 }
 
 }  // namespace esphome::runtime_image

esphome/components/runtime_image/jpeg_decoder.h

@@ -22,19 +22,41 @@ class JpegDecoder : public ImageDecoder {
   ~JpegDecoder() override {}
 
   int HOT decode(uint8_t *buffer, size_t size) override;
+  void reset() override;
+
+  /// The source is read as the decode needs it, through JPEGDEC's own 2 KB buffer
+  bool supports_source() const override { return true; }
+  int begin_source(DecodeSource *source) override;
+  /// Decodes one row of MCUs (8 or 16 pixel rows), or waits part way through one for more of the source
+  int HOT decode_step() override;
 
   bool uses_direct_rgb565() const { return this->direct_rgb565_; }
+  /// JPEGDEC decodes the image at 1/get_scale() of its size: 1, 2, 4 or 8
+  int get_scale() const { return this->scale_; }
   void draw_rgb565(int x, int y, int w, int h, const uint8_t *pixels);
 
  protected:
   bool prepare_rgb565_scaling_(int width, int height);
+  /// Set up an opened image for decoding. Returns 0, or a DecodeError.
+  int start_();
+  /// The JPEGDEC option for scale_: JPEG_SCALE_HALF, _QUARTER and _EIGHTH are the divisors themselves
+  int scale_option_() const { return this->scale_ == 1 ? 0 : this->scale_; }
+  /// The DecodeError for a failed read of the source or JPEGDEC's last error, closing the image
+  int fail_();
+
+  static int32_t source_read(JPEGFILE *file, uint8_t *buf, int32_t len);
+  static int32_t source_seek(JPEGFILE *file, int32_t position);
+  static void source_close(void *handle) {}
 
   JPEGDEC jpeg_{};
   FixedVector<uint16_t> x_boundaries_{};
   FixedVector<uint16_t> y_boundaries_{};
   int source_width_{0};
   int source_height_{0};
+  int scale_{1};                   // JPEGDEC decodes at 1/scale_ of the image size
+  DecodeSource *source_{nullptr};  // Set while a begin_source() decode is in progress
   bool direct_rgb565_{false};
+  bool source_failed_{false};
 };
 
 }  // namespace esphome::runtime_image

esphome/components/runtime_image/runtime_image.cpp

@@ -116,7 +116,9 @@ void RuntimeImage::draw_pixel(int x, int y, const Color &color) {
     }
     case image::IMAGE_TYPE_GRAYSCALE: {
       uint32_t pos = this->get_position_(x, y);
-      auto gray = static_cast<uint8_t>(0.2125 * color.r + 0.7154 * color.g + 0.0721 * color.b);
+      // 0.2125, 0.7154 and 0.0721 in 1/256ths, summing to 256 so white stays 255. Integer maths: the S3 has no
+      // double FPU
+      auto gray = static_cast<uint8_t>((54 * color.r + 183 * color.g + 19 * color.b) >> 8);
       if (this->transparency_ == image::TRANSPARENCY_CHROMA_KEY) {
         if (gray == 1) {
           gray = 0;
@@ -239,6 +241,25 @@ int RuntimeImage::feed_data(uint8_t *data, size_t len) {
   return consumed;
 }
 
+int RuntimeImage::begin_source(DecodeSource *source) {
+  if (!this->decoder_supports_source()) {
+    ESP_LOGE(TAG, "Decoder cannot read a source");
+    return DECODE_ERROR_UNSUPPORTED_FORMAT;
+  }
+  return this->decoder_->begin_source(source);
+}
+
+int RuntimeImage::decode_step() {
+  if (!this->is_decoding()) {
+    ESP_LOGE(TAG, "No decoder initialized");
+    return DECODE_ERROR_INVALID_TYPE;
+  }
+  const int result = this->decoder_->decode_step();
+  if (result == DECODE_STEP_DONE)
+    this->decoded_bytes_ = this->decoder_->get_decoded_bytes();
+  return result;
+}
+
 bool RuntimeImage::end_decode() {
   if (!this->is_decoding()) {
     return false;

esphome/components/runtime_image/runtime_image.h

@@ -76,6 +76,22 @@ class RuntimeImage : public image::Image {
    */
   int feed_data(uint8_t *data, size_t len);
 
+  /// Whether the active decoder can read a DecodeSource itself (see begin_source()).
+  bool decoder_supports_source() const { return this->is_decoding() && this->decoder_->supports_source(); }
+
+  /**
+   * @brief Decode from a source the decoder reads itself, in place of feed_data().
+   *
+   * Call after begin_decode() when decoder_supports_source() is true, once the image headers can be read from the
+   * source, then call decode_step() until it
+   * returns DECODE_STEP_DONE, and finish with end_decode().
+   * @return 0 on success, or a DecodeError value.
+   */
+  int begin_source(DecodeSource *source);
+
+  /// Decode a little more from the source; see ImageDecoder::decode_step().
+  int decode_step();
+
   /**
    * @brief Complete the decoding process.
    *

esphome/components/usb_uart/__init__.py

@@ -1,3 +1,5 @@
+from collections.abc import Callable
+
 import esphome.codegen as cg
 from esphome.components.const import CONF_DATA_BITS, CONF_PARITY, CONF_STOP_BITS
 from esphome.components.esp32 import VARIANT_ESP32P4, get_esp32_variant
@@ -154,6 +156,19 @@ FILTER_SOURCE_FILES = filter_source_files_from_defines(
 )
 
 
+def _channel_limit(type_: Type) -> Callable[[list], list]:
+    """Check the channel count against the type's limit, which depends on the target."""
+
+    def validator(value: list) -> list:
+        if len(value) > (limit := type_.max_channels):
+            raise cv.Invalid(
+                f"Device type {type_.name} supports a maximum of {limit} channels"
+            )
+        return value
+
+    return validator
+
+
 def channel_schema(type_: "Type") -> cv.Schema:
     schema = cv.Schema(
         {
@@ -192,10 +207,7 @@ def channel_schema(type_: "Type") -> cv.Schema:
                         }
                     )
                 ),
-                cv.Length(
-                    max=type_.max_channels,
-                    msg=f"Device type {type_.name} supports a maximum of {type_.max_channels} channels",
-                ),
+                _channel_limit(type_),
             ),
         }
     )

esphome/components/wifi/__init__.py

@@ -9,6 +9,7 @@ from esphome.components.esp32 import (
     add_idf_sdkconfig_option,
     const,
     get_esp32_variant,
+    idf_version,
     only_on_variant,
     request_wifi,
     require_mbedtls_tls,
@@ -65,7 +66,6 @@ from esphome.const import (
     CONF_USE_ADDRESS,
     CONF_USERNAME,
     PLACEHOLDER_WIFI_SSID,
-    Framework,
     Platform,
     PlatformFramework,
 )
@@ -232,11 +232,8 @@ def _validate_ap_mode(value: str) -> str:
 def _validate_dns_servers(value: list) -> list:
     if any(ip.is_unspecified for ip in value):
         raise cv.Invalid("0.0.0.0 is not a DNS server the access point can offer")
-    if len(value) > 1:
-        cv.require_framework_version(
-            esp_idf=cv.Version(6, 0, 0),
-            extra_message="The access point offers a second DNS server from ESP-IDF 6.0",
-        )(value)
+    if len(value) > 1 and CORE.is_esp32 and idf_version() < cv.Version(6, 0, 0):
+        raise cv.Invalid("The access point offers a second DNS server from ESP-IDF 6.0")
     return value
 
 
@@ -645,7 +642,6 @@ def _lease_cache_schema(value: Any) -> ConfigType:
     value = LEASE_CACHE_SCHEMA(value)
     if value[CONF_ENABLED]:
         cv.only_on_esp32(value)
-        cv.only_with_framework(Framework.ESP_IDF)(value)
         if CONF_STORAGE not in value:
             if not preferences.rtc_supported():
                 raise cv.Invalid(

platformio.ini

@@ -48,7 +48,7 @@ lib_deps =
     improv/Improv@1.2.7                    ; improv_serial / improv_ble
     kikuchan98/pngle@1.1.0                 ; runtime_image
     ; Using the repository directly, otherwise ESP-IDF can't use the library
-    https://github.com/bitbank2/JPEGDEC.git#1.8.4    ; runtime_image
+    https://github.com/esphome-libs/JPEGDEC.git#1.8.4-esphome.3    ; runtime_image
     ; This dependency is used only in unit tests.
     ; Must coincide with PLATFORMIO_GOOGLE_TEST_LIB in scripts/cpp_unit_test.py
     ; See scripts/cpp_unit_test.py and tests/components/README.md
@@ -253,7 +253,7 @@ lib_deps =
     heman/AsyncMqttClient-esphome@2.0.0   ; mqtt
     improv/Improv@1.2.7                   ; improv_serial
     kikuchan98/pngle@1.1.0                ; runtime_image
-    https://github.com/bitbank2/JPEGDEC.git#1.8.4    ; runtime_image
+    https://github.com/esphome-libs/JPEGDEC.git#1.8.4-esphome.3    ; runtime_image
 build_flags =
     ${common:arduino.build_flags}
     -DUSE_LIBRETINY

requirements.txt

@@ -31,9 +31,9 @@ smp==4.2.0; platform_system != "Darwin" or platform_machine != "x86_64"
 smp==4.1.0; platform_system == "Darwin" and platform_machine == "x86_64"
 requests==2.34.2
 py7zr==1.1.4
-platformdirs==4.13.4  # native esp-idf toolchain global cache dir
+platformdirs==4.13.5  # native esp-idf toolchain global cache dir
 ninja==1.13.2  # native host and esp8266 arduino toolchain build driver
-filelock==4.2.2  # inter-process locks (PlatformIO cache heal, git clone cache); >=3.32 for FileLock(fallback_to_soft=...), older versions silently drop the kwarg
+filelock==4.2.4  # inter-process locks (PlatformIO cache heal, git clone cache); >=3.32 for FileLock(fallback_to_soft=...), older versions silently drop the kwarg
 
 # esp-idf >= 5.0 requires this
 pyparsing >= 3.3.3

requirements_test.txt

@@ -1,7 +1,7 @@
 pylint==4.1.3
 ruff==0.17.1  # .pre-commit-config.yaml rev synced by script/sync_dependency_versions.py
 pyupgrade==3.22.0  # .pre-commit-config.yaml rev synced by script/sync_dependency_versions.py
-prek==0.5.5  # .github/workflows/ci.yml reads this pin
+prek==0.5.6  # .github/workflows/ci.yml reads this pin
 yamlrocks==0.7.1  # used by script/sync_dependency_versions.py
 
 # Unit tests

tests/component_tests/usb_uart/test_channel_limit.py

@@ -0,0 +1,38 @@
+"""Tests for the per-type channel limit, which depends on the target."""
+
+from pathlib import Path
+import subprocess
+import sys
+
+import pytest
+
+from esphome.components.esp32.const import KEY_VARIANT, VARIANT_ESP32, VARIANT_ESP32P4
+from esphome.components.usb_uart import channel_schema, uart_types
+import esphome.config_validation as cv
+from esphome.const import CONF_BAUD_RATE, CONF_CHANNELS, PlatformFramework
+from tests.component_tests.types import SetCoreConfigCallable
+
+CH34X = next(t for t in uart_types if t.name == "CH34X")
+
+
+def test_import_needs_no_core_config() -> None:
+    """The C++ unit test runner imports every component before any config is loaded."""
+    subprocess.run(
+        [sys.executable, "-c", "from esphome.components import usb_uart"],
+        cwd=Path(__file__).parents[3],
+        check=True,
+    )
+
+
+@pytest.mark.parametrize(
+    ("variant", "limit"), [(VARIANT_ESP32, 3), (VARIANT_ESP32P4, 4)]
+)
+def test_channel_limit_follows_the_target(
+    set_core_config: SetCoreConfigCallable, variant: str, limit: int
+) -> None:
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data={KEY_VARIANT: variant})
+    schema = channel_schema(CH34X)
+    channel = {CONF_BAUD_RATE: 9600}
+    assert len(schema({CONF_CHANNELS: [channel] * limit})[CONF_CHANNELS]) == limit
+    with pytest.raises(cv.Invalid, match=f"maximum of {limit} channels"):
+        schema({CONF_CHANNELS: [channel] * (limit + 1)})

tests/component_tests/wifi/test_lease_cache.py

@@ -21,14 +21,24 @@ def _validate(lease_cache: dict) -> dict:
     )
 
 
-def test_storage_defaults_to_rtc(set_core_config: SetCoreConfigCallable) -> None:
-    set_core_config(
-        PlatformFramework.ESP32_IDF, platform_data={KEY_VARIANT: VARIANT_ESP32}
-    )
+@pytest.mark.parametrize(
+    "framework", [PlatformFramework.ESP32_IDF, PlatformFramework.ESP32_ARDUINO]
+)
+def test_storage_defaults_to_rtc(
+    set_core_config: SetCoreConfigCallable, framework: PlatformFramework
+) -> None:
+    """Both ESP32 frameworks share the backend the cache lives in."""
+    set_core_config(framework, platform_data={KEY_VARIANT: VARIANT_ESP32})
     config = _validate({"max_age": "12h"})
     assert config["lease_cache"]["storage"] == "rtc"
 
 
+def test_lease_cache_requires_esp32(set_core_config: SetCoreConfigCallable) -> None:
+    set_core_config(PlatformFramework.ESP8266_ARDUINO)
+    with pytest.raises(cv.Invalid, match="only available on"):
+        _validate({"max_age": "12h"})
+
+
 def test_no_rtc_variant_requires_flash(set_core_config: SetCoreConfigCallable) -> None:
     """A variant without RTC memory must say storage: flash; the error points at that key."""
     set_core_config(

tests/components/mqtt/common.yaml

@@ -257,6 +257,8 @@ cover:
       - logger.log: position_action
     tilt_action:
       - logger.log: tilt_action
+    stop_tilt_action:
+      - logger.log: stop_tilt_action
     open_action:
       - logger.log: open_action
     close_action:

tests/components/online_image/common.yaml

@@ -19,6 +19,11 @@ image:
         } else {
           ESP_LOGD("online_image", "Cache miss: fresh download");
         }
+    on_download_started:
+      - logger.log: Download started
+    on_download_progress:
+      lambda: |-
+        ESP_LOGD("online_image", "Downloaded %.0f%% (%zu bytes)", progress, bytes_read);
   - platform: online_image
     id: online_binary_transparent_image
     url: http://www.libpng.org/pub/png/img_png/pnglogo-blk-tiny.png

tests/components/online_image/test_download_end.cpp

@@ -2,6 +2,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cmath>
 #include <cstdint>
 #include <cstring>
 #include <memory>
@@ -27,6 +28,9 @@ class FakeContainer : public http_request::HttpContainer {
   }
 
   int read(uint8_t *buf, size_t max_len) override {
+    this->largest_read = std::max(this->largest_read, max_len);
+    if (this->read_error_)
+      return -1;
     size_t len = std::min(max_len, this->available_ - this->bytes_read_);
     std::memcpy(buf, this->body_.data() + this->bytes_read_, len);
     this->bytes_read_ += len;
@@ -42,13 +46,21 @@ class FakeContainer : public http_request::HttpContainer {
   }
 
   void set_content_length(size_t length) { this->content_length = length; }
+  /// Make every read from now on fail, like a dropped connection
+  void fail_reads() { this->read_error_ = true; }
+  /// Let len more bytes of the body arrive
+  void deliver(size_t len) { this->available_ = std::min(this->body_.size(), this->available_ + len); }
   void add_response_header(const std::string &name, const std::string &value) {
     this->response_headers_.push_back({name, value});
   }
 
+  /// The most bytes any one read() asked for
+  size_t largest_read{0};
+
  protected:
   std::vector<uint8_t> body_;
   size_t available_;
+  bool read_error_{false};
 };
 
 class FakeHttpRequest : public http_request::HttpRequestComponent {
@@ -123,13 +135,173 @@ static constexpr std::array<uint8_t, 69> PNG_1X1{
     0x0C, 0x49, 0x44, 0x41, 0x54, 0x78, 0x9C, 0x63, 0xF8, 0xCF, 0xC0, 0x00, 0x00, 0x03, 0x01, 0x01, 0x00, 0xC9,
     0xFE, 0x92, 0xEF, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4E, 0x44, 0xAE, 0x42, 0x60, 0x82};
 
+// 8x8 progressive JPEG, 521 bytes
+static const uint8_t JPEG_PROGRESSIVE[] = {
+    0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00,
+    0x00, 0xFF, 0xDB, 0x00, 0x43, 0x00, 0x10, 0x0B, 0x0C, 0x0E, 0x0C, 0x0A, 0x10, 0x0E, 0x0D, 0x0E, 0x12, 0x11, 0x10,
+    0x13, 0x18, 0x28, 0x1A, 0x18, 0x16, 0x16, 0x18, 0x31, 0x23, 0x25, 0x1D, 0x28, 0x3A, 0x33, 0x3D, 0x3C, 0x39, 0x33,
+    0x38, 0x37, 0x40, 0x48, 0x5C, 0x4E, 0x40, 0x44, 0x57, 0x45, 0x37, 0x38, 0x50, 0x6D, 0x51, 0x57, 0x5F, 0x62, 0x67,
+    0x68, 0x67, 0x3E, 0x4D, 0x71, 0x79, 0x70, 0x64, 0x78, 0x5C, 0x65, 0x67, 0x63, 0xFF, 0xDB, 0x00, 0x43, 0x01, 0x11,
+    0x12, 0x12, 0x18, 0x15, 0x18, 0x2F, 0x1A, 0x1A, 0x2F, 0x63, 0x42, 0x38, 0x42, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63,
+    0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63,
+    0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63,
+    0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0xFF, 0xC2, 0x00, 0x11, 0x08, 0x00, 0x08, 0x00, 0x08, 0x03, 0x01, 0x22, 0x00,
+    0x02, 0x11, 0x01, 0x03, 0x11, 0x01, 0xFF, 0xC4, 0x00, 0x15, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0xFF, 0xC4, 0x00, 0x15, 0x01, 0x01, 0x01, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x05, 0xFF, 0xDA, 0x00, 0x0C, 0x03,
+    0x01, 0x00, 0x02, 0x10, 0x03, 0x10, 0x00, 0x00, 0x01, 0x94, 0x05, 0x3F, 0xFF, 0xC4, 0x00, 0x14, 0x10, 0x01, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08,
+    0x01, 0x01, 0x00, 0x01, 0x05, 0x02, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01, 0x03, 0x01, 0x01, 0x3F,
+    0x01, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01, 0x02, 0x01, 0x01, 0x3F, 0x01, 0x7F, 0xFF, 0xC4, 0x00,
+    0x14, 0x10, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0xFF, 0xDA, 0x00, 0x08, 0x01, 0x01, 0x00, 0x06, 0x3F, 0x02, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x10, 0x01, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01,
+    0x01, 0x00, 0x01, 0x3F, 0x21, 0x7F, 0xFF, 0xDA, 0x00, 0x0C, 0x03, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x00, 0x00,
+    0x10, 0x0B, 0xFF, 0xC4, 0x00, 0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01, 0x03, 0x01, 0x01, 0x3F, 0x10, 0x7F, 0xFF, 0xC4, 0x00,
+    0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0xFF, 0xDA, 0x00, 0x08, 0x01, 0x02, 0x01, 0x01, 0x3F, 0x10, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x10, 0x01, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01,
+    0x01, 0x00, 0x01, 0x3F, 0x10, 0x7F, 0xFF, 0xD9,
+};
+
+// 48x40 4:2:0 JPEG (quality 95), 2344 bytes: three rows of 16 pixel MCUs, with the scan starting at byte 609
+static const uint8_t JPEG_48X40[] = {
+    0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00,
+    0x00, 0xFF, 0xDB, 0x00, 0x43, 0x00, 0x02, 0x01, 0x01, 0x01, 0x01, 0x01, 0x02, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02,
+    0x02, 0x02, 0x04, 0x03, 0x02, 0x02, 0x02, 0x02, 0x05, 0x04, 0x04, 0x03, 0x04, 0x06, 0x05, 0x06, 0x06, 0x06, 0x05,
+    0x06, 0x06, 0x06, 0x07, 0x09, 0x08, 0x06, 0x07, 0x09, 0x07, 0x06, 0x06, 0x08, 0x0B, 0x08, 0x09, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x06, 0x08, 0x0B, 0x0C, 0x0B, 0x0A, 0x0C, 0x09, 0x0A, 0x0A, 0x0A, 0xFF, 0xDB, 0x00, 0x43, 0x01, 0x02,
+    0x02, 0x02, 0x02, 0x02, 0x02, 0x05, 0x03, 0x03, 0x05, 0x0A, 0x07, 0x06, 0x07, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0xFF, 0xC0, 0x00, 0x11, 0x08, 0x00, 0x28, 0x00, 0x30, 0x03, 0x01, 0x22, 0x00,
+    0x02, 0x11, 0x01, 0x03, 0x11, 0x01, 0xFF, 0xC4, 0x00, 0x1F, 0x00, 0x00, 0x01, 0x05, 0x01, 0x01, 0x01, 0x01, 0x01,
+    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A,
+    0x0B, 0xFF, 0xC4, 0x00, 0xB5, 0x10, 0x00, 0x02, 0x01, 0x03, 0x03, 0x02, 0x04, 0x03, 0x05, 0x05, 0x04, 0x04, 0x00,
+    0x00, 0x01, 0x7D, 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12, 0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
+    0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xA1, 0x08, 0x23, 0x42, 0xB1, 0xC1, 0x15, 0x52, 0xD1, 0xF0, 0x24, 0x33, 0x62,
+    0x72, 0x82, 0x09, 0x0A, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x34, 0x35, 0x36, 0x37,
+    0x38, 0x39, 0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A,
+    0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x83, 0x84, 0x85,
+    0x86, 0x87, 0x88, 0x89, 0x8A, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6,
+    0xA7, 0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7,
+    0xC8, 0xC9, 0xCA, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7,
+    0xE8, 0xE9, 0xEA, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFF, 0xC4, 0x00, 0x1F, 0x01, 0x00,
+    0x03, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03,
+    0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0xFF, 0xC4, 0x00, 0xB5, 0x11, 0x00, 0x02, 0x01, 0x02, 0x04, 0x04,
+    0x03, 0x04, 0x07, 0x05, 0x04, 0x04, 0x00, 0x01, 0x02, 0x77, 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21, 0x31,
+    0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71, 0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91, 0xA1, 0xB1, 0xC1, 0x09,
+    0x23, 0x33, 0x52, 0xF0, 0x15, 0x62, 0x72, 0xD1, 0x0A, 0x16, 0x24, 0x34, 0xE1, 0x25, 0xF1, 0x17, 0x18, 0x19, 0x1A,
+    0x26, 0x27, 0x28, 0x29, 0x2A, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A,
+    0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x73, 0x74, 0x75,
+    0x76, 0x77, 0x78, 0x79, 0x7A, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x92, 0x93, 0x94, 0x95, 0x96,
+    0x97, 0x98, 0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7,
+    0xB8, 0xB9, 0xBA, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8,
+    0xD9, 0xDA, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9,
+    0xFA, 0xFF, 0xDA, 0x00, 0x0C, 0x03, 0x01, 0x00, 0x02, 0x11, 0x03, 0x11, 0x00, 0x3F, 0x00, 0xFC, 0xAA, 0xB8, 0xB7,
+    0xD3, 0xB5, 0xD8, 0x1E, 0xD6, 0xD1, 0xA5, 0x5B, 0x4B, 0x46, 0x10, 0xC1, 0x06, 0xA1, 0x29, 0x69, 0x25, 0xB7, 0xC2,
+    0xC6, 0x0C, 0x71, 0x26, 0x5E, 0x50, 0x15, 0x5D, 0xB6, 0x9C, 0x9E, 0x00, 0xC1, 0x67, 0x67, 0x4D, 0xCF, 0x84, 0xF7,
+    0x57, 0xA6, 0xDA, 0x08, 0x52, 0xF5, 0xE5, 0xBA, 0xB8, 0x7B, 0x5B, 0x68, 0xEE, 0x2F, 0x66, 0x89, 0xB7, 0xB7, 0x9B,
+    0xE5, 0x9C, 0x23, 0xAA, 0xFE, 0xF7, 0x68, 0x11, 0x9E, 0x5D, 0x18, 0x12, 0x48, 0x56, 0x5C, 0x9F, 0x57, 0xB6, 0xF8,
+    0x33, 0xF0, 0xE2, 0x5B, 0xFB, 0xCF, 0xF4, 0x51, 0x0C, 0xC6, 0x64, 0x30, 0x49, 0x71, 0x7C, 0xE2, 0x16, 0x90, 0x2E,
+    0xF4, 0x72, 0xEA, 0xE0, 0x34, 0x81, 0x77, 0x93, 0x9C, 0x07, 0xC2, 0x93, 0xB9, 0x61, 0xC0, 0xD3, 0xF0, 0x17, 0xC1,
+    0xBF, 0x03, 0xCD, 0xE1, 0xAD, 0x42, 0x3F, 0x0A, 0xD8, 0xC7, 0x2D, 0xAC, 0x36, 0xCB, 0xF6, 0x79, 0x22, 0x69, 0x84,
+    0xC4, 0x93, 0x29, 0x2A, 0x89, 0xB9, 0x00, 0x50, 0x62, 0x7C, 0xFF, 0x00, 0x16, 0xD9, 0x65, 0x00, 0x16, 0x65, 0x07,
+    0xFA, 0x5B, 0x36, 0xE2, 0xAC, 0xBF, 0x2D, 0x55, 0x79, 0x29, 0xB5, 0x26, 0x9B, 0xA9, 0x18, 0xB5, 0x15, 0x36, 0x9B,
+    0x53, 0xD1, 0xCA, 0x10, 0x93, 0x69, 0xB6, 0x94, 0x27, 0x16, 0xAF, 0x19, 0x29, 0xB8, 0xBB, 0x3F, 0x9A, 0xE1, 0x1E,
+    0x2A, 0xCB, 0x9E, 0x79, 0x4A, 0x92, 0x84, 0xDA, 0xD6, 0xED, 0xA4, 0xED, 0x7A, 0x72, 0xB5, 0xAC, 0xF6, 0xEB, 0xAD,
+    0xD5, 0x97, 0x91, 0xC9, 0x4D, 0xA4, 0xE9, 0xD7, 0x56, 0x45, 0x66, 0xD3, 0x9D, 0x85, 0xB1, 0x86, 0x59, 0x7E, 0xD9,
+    0x7E, 0xA0, 0xE0, 0xA8, 0x02, 0x17, 0x02, 0x3C, 0x36, 0x59, 0x18, 0xE2, 0x42, 0x1D, 0x40, 0x56, 0x0A, 0x77, 0x30,
+    0xAE, 0xFA, 0x56, 0xD4, 0xA4, 0x8A, 0xD9, 0xAD, 0xD6, 0x38, 0x1D, 0x7F, 0x77, 0x77, 0x1C, 0xB2, 0x4C, 0x22, 0x8C,
+    0x2B, 0xF3, 0x14, 0x64, 0x45, 0x85, 0x52, 0x47, 0x92, 0x7E, 0xF2, 0x0F, 0x34, 0x1D, 0xBC, 0x56, 0xDE, 0x85, 0xF0,
+    0x4B, 0xE1, 0x0A, 0xE9, 0xB0, 0xDB, 0x2D, 0x8C, 0x4C, 0xCD, 0x74, 0xF1, 0x42, 0x96, 0x93, 0xCF, 0xF6, 0x54, 0x0C,
+    0xB3, 0x44, 0x03, 0xAA, 0x6C, 0x49, 0x10, 0x87, 0x00, 0x88, 0xC2, 0xEE, 0x66, 0x6F, 0x9B, 0xAB, 0x57, 0xA4, 0x68,
+    0xDF, 0x0A, 0x3E, 0x1B, 0xDA, 0xE9, 0xDF, 0xD9, 0x96, 0xFE, 0x03, 0xB2, 0x8E, 0xD9, 0x8A, 0xDD, 0xC1, 0x77, 0x14,
+    0x97, 0x50, 0x2E, 0xE3, 0x20, 0x62, 0xA0, 0x33, 0x0C, 0xC6, 0x58, 0x48, 0x36, 0x6D, 0xC1, 0x20, 0xA2, 0x2B, 0x00,
+    0xB5, 0xF1, 0x99, 0xCF, 0x19, 0x65, 0x79, 0xAD, 0x0C, 0x3C, 0x2B, 0x61, 0xF9, 0x28, 0xD6, 0x52, 0x97, 0x35, 0x95,
+    0xD4, 0x61, 0x28, 0x5B, 0x99, 0xB8, 0xA9, 0xA9, 0x47, 0xD9, 0x3A, 0x69, 0xA9, 0xC6, 0x51, 0x52, 0x6A, 0x0D, 0x4A,
+    0x74, 0xA9, 0xC3, 0xFA, 0x7F, 0xC3, 0xFE, 0x25, 0xC1, 0x4E, 0xAE, 0x26, 0x2E, 0x13, 0x71, 0x5C, 0x8D, 0xFB, 0xB1,
+    0xD6, 0xEA, 0x6F, 0xF9, 0xAF, 0xBE, 0xB7, 0x4B, 0x55, 0x1D, 0x75, 0x4C, 0xF3, 0xDF, 0x05, 0xD9, 0xF8, 0x7B, 0xC3,
+    0xBA, 0xB5, 0xF1, 0xBC, 0x8D, 0x63, 0xDF, 0x1C, 0x32, 0x88, 0x1A, 0xF3, 0x74, 0x73, 0x89, 0x15, 0xC4, 0x8A, 0x25,
+    0x66, 0xDC, 0xAA, 0x98, 0x60, 0x06, 0x7F, 0xBD, 0xF2, 0x81, 0xF3, 0x36, 0xFE, 0x9D, 0xAF, 0x78, 0x8F, 0x54, 0xD3,
+    0xAD, 0xA6, 0x9E, 0xC5, 0xE5, 0x9C, 0x96, 0xDC, 0xB7, 0xE8, 0x84, 0x47, 0xFB, 0xB4, 0x54, 0x42, 0x0F, 0x03, 0xF8,
+    0xD7, 0xE5, 0x39, 0x60, 0xF8, 0x04, 0x79, 0x7B, 0xE3, 0xF4, 0x9F, 0x85, 0x5F, 0x08, 0xBE, 0x0D, 0x2C, 0x57, 0xCE,
+    0x6C, 0xA5, 0x2B, 0xA8, 0x08, 0x20, 0x82, 0x04, 0xB9, 0xB8, 0x82, 0x43, 0x28, 0x72, 0x55, 0xD5, 0x83, 0xB9, 0x05,
+    0xC2, 0x44, 0x55, 0x77, 0x8C, 0xFC, 0xEC, 0xD8, 0xCB, 0xE7, 0xBE, 0x9B, 0xE0, 0x5F, 0xC3, 0x9D, 0x32, 0xD4, 0x45,
+    0x26, 0x8B, 0x2C, 0x93, 0xC0, 0xF3, 0x95, 0x49, 0xEE, 0x2E, 0x0C, 0x26, 0x26, 0x31, 0xC9, 0xF3, 0xED, 0x95, 0x96,
+    0x32, 0xEC, 0x10, 0xE1, 0xB8, 0x60, 0x3A, 0x90, 0x1B, 0x3F, 0x9E, 0x66, 0x58, 0xFC, 0x14, 0x31, 0x15, 0xFD, 0x9C,
+    0x79, 0x57, 0x3A, 0x92, 0x84, 0x1C, 0x3D, 0xC9, 0xCD, 0x27, 0x6D, 0x12, 0xE5, 0xE7, 0xA6, 0xD5, 0x4D, 0x64, 0x93,
+    0xD1, 0x45, 0xC6, 0xAD, 0xE7, 0x2F, 0xE9, 0xEE, 0x17, 0xE3, 0x0C, 0x0A, 0xE1, 0x9C, 0x37, 0x34, 0x67, 0x2B, 0x73,
+    0x2B, 0xB4, 0xBA, 0x49, 0xF4, 0x72, 0x57, 0x51, 0xDD, 0x24, 0x9B, 0x5A, 0x36, 0x9A, 0x49, 0x1E, 0x15, 0xA7, 0x7E,
+    0xCE, 0xF6, 0x89, 0x6A, 0x96, 0x43, 0x55, 0xB5, 0xB3, 0xB6, 0xB8, 0x96, 0x2B, 0x9B, 0x78, 0xA0, 0xB4, 0x9E, 0xE5,
+    0x61, 0x90, 0xE0, 0xC2, 0xEC, 0x61, 0x91, 0x47, 0xCC, 0xDB, 0xF1, 0x80, 0xC0, 0x98, 0xD4, 0xE5, 0xDC, 0x64, 0xEC,
+    0x7C, 0x29, 0xFD, 0x98, 0x6C, 0xAF, 0xEC, 0xF5, 0x76, 0xB7, 0xF1, 0x36, 0x9A, 0x5D, 0x6F, 0x96, 0xE1, 0x74, 0xB5,
+    0xD3, 0x44, 0x91, 0xA8, 0x45, 0x0C, 0xE2, 0x3D, 0xAC, 0x85, 0xF9, 0x3B, 0x5B, 0x19, 0x8A, 0x43, 0x1F, 0xCA, 0x50,
+    0x9D, 0x87, 0xD2, 0x0F, 0xC2, 0x1F, 0x89, 0x4F, 0x6D, 0x04, 0x0F, 0xE1, 0x61, 0xAA, 0xEE, 0xB4, 0x8E, 0x56, 0xFB,
+    0x06, 0xAF, 0x04, 0xF3, 0x40, 0x9B, 0x55, 0x4E, 0xCB, 0x66, 0x91, 0xCB, 0x18, 0xC2, 0x88, 0xB6, 0xB1, 0x65, 0x60,
+    0xA4, 0x6E, 0xDC, 0xA4, 0x9E, 0xAF, 0xE1, 0xBF, 0xC2, 0x2F, 0x89, 0xA9, 0xE1, 0xFB, 0x8D, 0x6E, 0xC2, 0x3B, 0x4B,
+    0x30, 0xD7, 0x60, 0xDA, 0x41, 0x2D, 0xCC, 0x6C, 0x2E, 0x49, 0xF3, 0x1E, 0x42, 0x19, 0x5D, 0x58, 0x3C, 0x8A, 0x81,
+    0x82, 0xB8, 0x0C, 0xC9, 0xF2, 0xE5, 0x8F, 0x03, 0x8F, 0x36, 0xE3, 0x8A, 0x98, 0xCC, 0x14, 0xAB, 0x62, 0x2B, 0xC2,
+    0x34, 0xA2, 0xA5, 0x78, 0x37, 0x42, 0x12, 0x70, 0x8C, 0x62, 0xD2, 0x6D, 0x72, 0x7B, 0xAF, 0x9B, 0xDD, 0xFD, 0xE5,
+    0x4E, 0x79, 0x49, 0x45, 0x73, 0xA9, 0x72, 0x2F, 0xF0, 0x73, 0x83, 0xF8, 0xCE, 0xB4, 0x33, 0xE8, 0x3F, 0xAE, 0x42,
+    0xF7, 0x76, 0xB3, 0x83, 0x57, 0xE5, 0x95, 0xBE, 0xCE, 0x8F, 0x7B, 0xDE, 0xD7, 0x4B, 0x6B, 0x9C, 0x1E, 0x8D, 0xF0,
+    0x56, 0x7B, 0xDD, 0x26, 0x34, 0x5F, 0x1F, 0xDB, 0x9D, 0x37, 0x53, 0xB8, 0x96, 0xED, 0xA0, 0x16, 0xB1, 0xC9, 0x2C,
+    0x8B, 0xF2, 0x26, 0x58, 0x89, 0x37, 0xEE, 0x04, 0xB2, 0x97, 0x54, 0x2D, 0x88, 0xC0, 0x60, 0x0B, 0x03, 0x5E, 0x9B,
+    0x67, 0xFB, 0x36, 0xE9, 0x31, 0x2D, 0x9C, 0x37, 0x9E, 0x32, 0x84, 0x5D, 0x2C, 0x4A, 0xD6, 0xAD, 0x73, 0x63, 0x28,
+    0x36, 0xAA, 0x53, 0xF7, 0x90, 0x29, 0x8E, 0x5C, 0x92, 0xBE, 0x41, 0xDC, 0xC0, 0xB3, 0x2B, 0x46, 0x32, 0x4B, 0x96,
+    0x35, 0xAD, 0x1F, 0xC2, 0xDF, 0x89, 0x17, 0xF6, 0xB6, 0xFA, 0xB5, 0xED, 0xB8, 0xB7, 0x8E, 0x78, 0x66, 0x96, 0x09,
+    0x6C, 0x6E, 0x23, 0x32, 0x28, 0x08, 0xE8, 0xF2, 0xBA, 0xF9, 0x86, 0x48, 0xC0, 0x68, 0xFE, 0x63, 0xC8, 0x23, 0x82,
+    0xCC, 0xA5, 0x4A, 0xFA, 0x66, 0x8F, 0xF0, 0x37, 0xE2, 0x6D, 0xE5, 0xC9, 0x3A, 0x87, 0x86, 0xB4, 0xFB, 0x28, 0xAE,
+    0x61, 0x0F, 0x0B, 0x59, 0xDF, 0xC0, 0xD1, 0xAC, 0xE0, 0x24, 0x41, 0x42, 0xC4, 0x49, 0x1B, 0x10, 0x21, 0x50, 0xC0,
+    0x09, 0x11, 0x8B, 0xEE, 0x6E, 0x71, 0xE2, 0xE2, 0x78, 0xBB, 0x33, 0xFA, 0xC5, 0x1A, 0xB4, 0xEA, 0xC6, 0x74, 0xD2,
+    0x8C, 0x24, 0xA5, 0x2A, 0x3C, 0xB5, 0x2E, 0xB9, 0x9B, 0x71, 0x97, 0x34, 0xE0, 0xAA, 0x54, 0x93, 0x71, 0x56, 0x49,
+    0xB9, 0xC6, 0x4E, 0x9A, 0x9B, 0xD3, 0xFA, 0x7F, 0x81, 0xB8, 0xD6, 0xAC, 0xDD, 0x6F, 0x65, 0x8D, 0x82, 0x77, 0x85,
+    0x95, 0xE1, 0x7D, 0x1C, 0xD2, 0x8B, 0x7A, 0x27, 0xA2, 0xF4, 0xED, 0xEE, 0x9E, 0x67, 0xE0, 0x8F, 0x81, 0x37, 0xBA,
+    0xEF, 0x87, 0x67, 0xBF, 0x8F, 0xC4, 0xD2, 0xDD, 0x4F, 0x05, 0xA8, 0x61, 0x7B, 0x1E, 0x9E, 0xE1, 0x8C, 0xEA, 0xF3,
+    0x18, 0x99, 0xA3, 0xDE, 0x76, 0x66, 0x36, 0x2A, 0x30, 0xFB, 0x9B, 0x0F, 0xC3, 0x1C, 0xA3, 0x76, 0x4B, 0xFB, 0x3B,
+    0xE8, 0xBA, 0x66, 0xBF, 0x0E, 0x93, 0xFD, 0xAB, 0x23, 0xD9, 0xA5, 0xCE, 0x62, 0xF3, 0x34, 0xEB, 0x7F, 0x29, 0x0A,
+    0xA7, 0x04, 0x48, 0xF2, 0x79, 0x82, 0x42, 0x1D, 0x46, 0x4B, 0xA9, 0x1B, 0xD1, 0xBE, 0x52, 0x54, 0xD7, 0xA8, 0xF8,
+    0x33, 0xE1, 0xAF, 0xC4, 0xA8, 0x24, 0xD6, 0x6D, 0xED, 0xBC, 0x0A, 0xD3, 0x5A, 0x5C, 0xC4, 0xDF, 0x64, 0x17, 0x97,
+    0x36, 0xF0, 0x65, 0x52, 0x39, 0xD4, 0x23, 0x22, 0x9D, 0xD8, 0x64, 0x83, 0x04, 0x85, 0x38, 0xEF, 0xB8, 0x49, 0x91,
+    0xBB, 0xFF, 0x00, 0x0A, 0xDF, 0xE3, 0x77, 0x84, 0xAC, 0xD3, 0x4A, 0xBC, 0xF0, 0x3A, 0x5A, 0x5B, 0x4F, 0x72, 0x5E,
+    0xD7, 0x53, 0x8E, 0xE2, 0x12, 0x6D, 0xC6, 0x40, 0x20, 0x47, 0xE6, 0x3E, 0x71, 0x26, 0x70, 0x24, 0xE4, 0xB4, 0x63,
+    0x2A, 0xC0, 0xE0, 0x7E, 0x71, 0x98, 0x71, 0x35, 0x5C, 0x4E, 0x69, 0x5A, 0xBD, 0x7C, 0x7A, 0x9C, 0xE3, 0xC9, 0xCF,
+    0x38, 0x46, 0x8D, 0xA4, 0xDC, 0x63, 0x38, 0x4A, 0xE9, 0xED, 0x5A, 0x4E, 0x4A, 0x6D, 0xF3, 0xCA, 0x2D, 0xB9, 0x4D,
+    0xD3, 0x77, 0x8C, 0x7F, 0xA8, 0xF8, 0x53, 0x8D, 0x31, 0x32, 0xC8, 0xA9, 0xDB, 0x15, 0x04, 0x9F, 0xB4, 0xD2, 0xF4,
+    0xD3, 0xF8, 0xA5, 0x77, 0xCD, 0xB3, 0x49, 0x6C, 0xB4, 0xEA, 0x97, 0x46, 0x78, 0x45, 0xC4, 0x16, 0x5A, 0xDD, 0xA5,
+    0xA6, 0x8D, 0xA7, 0xEA, 0x77, 0x4A, 0x54, 0x47, 0x3C, 0x31, 0x41, 0x20, 0x06, 0x68, 0x00, 0x9A, 0x4F, 0x2A, 0x40,
+    0x5D, 0x5F, 0x69, 0xF3, 0x15, 0xCB, 0x32, 0x96, 0xDC, 0xC0, 0x90, 0xA5, 0xF0, 0xBD, 0xAF, 0xC3, 0x96, 0x83, 0x51,
+    0xB8, 0xD6, 0xA7, 0x48, 0xD2, 0xE8, 0x2B, 0x2C, 0x2D, 0x6B, 0xF6, 0xA4, 0x55, 0x8E, 0x45, 0x5F, 0xBA, 0x54, 0x2A,
+    0x36, 0x77, 0x12, 0x72, 0xE5, 0x9C, 0x14, 0x3B, 0x63, 0x6C, 0x62, 0x8A, 0x2B, 0xDE, 0xCD, 0x70, 0x74, 0xA7, 0x92,
+    0xE2, 0x31, 0x35, 0x2D, 0x29, 0x54, 0xBB, 0x97, 0xBB, 0x18, 0xF3, 0x38, 0x52, 0xA5, 0x38, 0xDF, 0x92, 0x31, 0x7E,
+    0xEB, 0x9B, 0x6A, 0xCD, 0x6B, 0xEF, 0x7C, 0x6E, 0x52, 0x7F, 0xE1, 0xF7, 0x0E, 0x54, 0x96, 0x1B, 0x3D, 0x52, 0x86,
+    0xF0, 0x73, 0x4B, 0xEE, 0x92, 0xD6, 0xD6, 0xBF, 0xC2, 0x8D, 0x9F, 0x0B, 0xDE, 0xEB, 0xF3, 0x69, 0x6B, 0x06, 0x9B,
+    0xA9, 0x5B, 0xE9, 0xF6, 0x6F, 0x76, 0x1E, 0x45, 0x8E, 0xE1, 0x54, 0xC8, 0xCD, 0xF3, 0x28, 0x8B, 0x1C, 0x9E, 0x25,
+    0x55, 0xDA, 0xA5, 0x58, 0x80, 0xCA, 0x46, 0x42, 0xA8, 0xF4, 0x1B, 0xEB, 0xBB, 0xBB, 0x8B, 0x69, 0xAF, 0xA5, 0x8E,
+    0xD0, 0x49, 0x25, 0x9C, 0x37, 0x73, 0xE9, 0xD7, 0xF2, 0x14, 0x8E, 0x55, 0x91, 0x64, 0x90, 0x46, 0xA8, 0xF9, 0x50,
+    0x57, 0x73, 0x2E, 0xE0, 0x55, 0xF6, 0x87, 0x45, 0x20, 0x2E, 0xC7, 0x28, 0xAF, 0xCD, 0x78, 0xA6, 0xA5, 0x5C, 0x26,
+    0x33, 0x01, 0x35, 0x2E, 0x67, 0x52, 0x35, 0xA0, 0xEE, 0x93, 0x56, 0x70, 0x4F, 0x48, 0xDB, 0x95, 0x6B, 0x76, 0xF4,
+    0xB4, 0xA5, 0x27, 0x29, 0x29, 0x35, 0x16, 0xBF, 0xA8, 0x7C, 0x3E, 0x92, 0xF6, 0x98, 0xA8, 0x5B, 0x4B, 0xC5, 0xDB,
+    0x5E, 0x8E, 0x4F, 0x7D, 0xFA, 0xDB, 0x57, 0xB2, 0x56, 0xD6, 0xED, 0xF7, 0x3E, 0x10, 0xB2, 0x82, 0xF6, 0xC2, 0xF2,
+    0xF3, 0x4E, 0xD4, 0xAF, 0xEE, 0x5A, 0xCA, 0xCE, 0xD2, 0xF1, 0xA7, 0xB8, 0x9D, 0xD4, 0x42, 0x8C, 0xF2, 0x3C, 0x8E,
+    0x42, 0x02, 0x24, 0xFD, 0xDA, 0x96, 0x60, 0xAD, 0xB0, 0xC9, 0x0E, 0x00, 0xC8, 0xC8, 0xEA, 0xEE, 0x12, 0x7B, 0x09,
+    0x6C, 0x6E, 0xCE, 0xA2, 0x0B, 0xAA, 0x32, 0xD9, 0xB9, 0x49, 0x66, 0xDF, 0x74, 0xCC, 0x31, 0x1B, 0xE4, 0xE6, 0x63,
+    0xF2, 0x91, 0x95, 0x42, 0x15, 0x8B, 0x7D, 0xE0, 0xAC, 0xB4, 0x51, 0x5F, 0x33, 0x3A, 0xD8, 0x8C, 0x46, 0x7A, 0x9C,
+    0xA6, 0xD7, 0x2C, 0x13, 0x49, 0x25, 0x6E, 0x6A, 0x73, 0xE4, 0x84, 0x9E, 0x9A, 0xC9, 0x29, 0x24, 0x9E, 0xE9, 0x42,
+    0x11, 0x8D, 0xA2, 0x9C, 0x5F, 0xF5, 0x37, 0x0D, 0x36, 0xF8, 0x7E, 0x9A, 0xEC, 0xE5, 0xE5, 0x7E, 0x67, 0x77, 0x7B,
+    0x7A, 0xBF, 0x5E, 0xB7, 0x3F, 0xFF, 0xD9,
+};
+
 static void set_loop_time(uint32_t now) { LoopBlockingGuard clock(nullptr, LOG_STR("test"), now); }
 
 class OnlineImageDownloadEnd : public ::testing::Test {
  protected:
-  std::unique_ptr<OnlineImage> make_image_(runtime_image::ImageFormat format) {
+  std::unique_ptr<OnlineImage> make_image_(runtime_image::ImageFormat format, uint32_t buffer_size = 256) {
     auto img = std::make_unique<OnlineImage>("http://example.com/image", 0, 0, format, image::IMAGE_TYPE_RGB,
-                                             image::TRANSPARENCY_OPAQUE, nullptr, 256);
+                                             image::TRANSPARENCY_OPAQUE, nullptr, buffer_size);
     img->set_parent(&this->http_);
     return img;
   }
@@ -286,4 +458,294 @@ TEST_F(OnlineImageDownloadEnd, JpegBufferAllocationFailureReportsError) {
   EXPECT_EQ(this->finished_, 0);
 }
 
+// The JPEG decoded with all of it in memory at once, to compare the downloaded images with
+static std::vector<uint8_t> reference_jpeg_pixels() {
+  runtime_image::RuntimeImage ref(runtime_image::JPEG, image::IMAGE_TYPE_RGB, image::TRANSPARENCY_OPAQUE);
+  std::vector<uint8_t> data(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40));
+  EXPECT_TRUE(ref.begin_decode(data.size()));
+  EXPECT_EQ(ref.feed_data(data.data(), data.size()), static_cast<int>(data.size()));
+  EXPECT_TRUE(ref.end_decode());
+  return std::vector<uint8_t>(ref.get_data_start(), ref.get_data_start() + ref.get_width_stride() * ref.get_height());
+}
+
+static std::vector<uint8_t> image_pixels(OnlineImage &image) {
+  return std::vector<uint8_t>(image.get_data_start(),
+                              image.get_data_start() + image.get_width_stride() * image.get_height());
+}
+
+// A JPEG of known size is decoded as it arrives, so a buffer smaller than the file only has to hold the headers
+TEST_F(OnlineImageDownloadEnd, JpegDecodesThroughASmallBuffer) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  // Bytes after the image are never needed. Waiting for the whole file before decoding would read them all.
+  std::vector<uint8_t> body(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40));
+  body.resize(body.size() + 8192, 0);
+  auto container = std::make_shared<FakeContainer>(body, body.size(), false);
+  container->add_response_header("etag", "\"abc\"");
+  this->start_(*image, container);
+
+  for (int i = 0; i < 100 && this->finished_ + this->errors_ == 0; i++)
+    image->loop();
+
+  ASSERT_EQ(this->finished_, 1);
+  EXPECT_LT(container->get_bytes_read(), body.size()) << "the image was not decoded as it arrived";
+  EXPECT_EQ(this->errors_, 0);
+  ASSERT_EQ(image->get_width(), 48);
+  ASSERT_EQ(image->get_height(), 40);
+  EXPECT_EQ(image_pixels(*image), reference_jpeg_pixels());
+
+  // A complete image is cached
+  this->http_.next = std::make_shared<FakeContainer>(std::vector<uint8_t>{}, 0, false);
+  image->update();
+  EXPECT_TRUE(this->http_.sent_header("if-none-match"));
+}
+
+// A read() waits for every byte it asks for, so a large buffer is filled a little at a time rather than in one
+// read that blocks the loop until the whole buffer has arrived
+TEST_F(OnlineImageDownloadEnd, JpegReadsInSmallPiecesWithALargeBuffer) {
+  auto image = this->make_image_(runtime_image::JPEG, 65536);
+  auto container =
+      std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)), 0, false);
+  this->start_(*image, container);
+
+  for (int i = 0; i < 100 && this->finished_ + this->errors_ == 0; i++) {
+    container->deliver(sizeof(JPEG_48X40));
+    image->loop();
+  }
+
+  ASSERT_EQ(this->finished_, 1);
+  EXPECT_EQ(this->errors_, 0);
+  EXPECT_LE(container->largest_read, READ_CHUNK);
+  EXPECT_EQ(image_pixels(*image), reference_jpeg_pixels());
+}
+
+// A downloaded PNG is read a little at a time too
+TEST_F(OnlineImageDownloadEnd, PngReadsInSmallPiecesWithALargeBuffer) {
+  auto image = this->make_image_(runtime_image::PNG, 65536);
+  std::vector<uint8_t> png(PNG_1X1.begin(), PNG_1X1.end());
+  auto container = std::make_shared<FakeContainer>(png, png.size(), false);
+  this->start_(*image, container);
+
+  for (int i = 0; i < 100 && this->finished_ + this->errors_ == 0; i++)
+    image->loop();
+
+  ASSERT_EQ(this->finished_, 1);
+  EXPECT_EQ(this->errors_, 0);
+  EXPECT_LE(container->largest_read, READ_CHUNK);
+}
+
+// A slow link: the decoder waits part way through the image for the rest to arrive
+TEST_F(OnlineImageDownloadEnd, JpegWaitsForASlowDownload) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  auto container =
+      std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)), 1024, false);
+  this->start_(*image, container);
+
+  int passes = 0;
+  for (; passes < 1000 && this->finished_ + this->errors_ == 0; passes++) {
+    image->loop();
+    if (passes == 5) {
+      EXPECT_EQ(this->finished_, 0) << "the image cannot be finished before the rest of it arrives";
+    }
+    container->deliver(40);
+  }
+
+  ASSERT_EQ(this->finished_, 1);
+  EXPECT_EQ(this->errors_, 0);
+  EXPECT_GT(passes, 10);
+  EXPECT_EQ(image_pixels(*image), reference_jpeg_pixels());
+}
+
+// A download that stops part way through times out rather than waiting for ever
+TEST_F(OnlineImageDownloadEnd, JpegDownloadThatStopsTimesOut) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  auto container =
+      std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)), 1500, false);
+  set_loop_time(1000);
+  this->start_(*image, container);
+
+  for (int i = 0; i < 10; i++)
+    image->loop();
+  EXPECT_EQ(this->errors_, 0) << "still within the timeout";
+
+  set_loop_time(1000 + this->http_.get_timeout());
+  image->loop();
+  EXPECT_EQ(this->errors_, 1);
+  EXPECT_EQ(this->finished_, 0);
+}
+
+// Headers that do not fit the download buffer cannot be read as the image arrives, so the whole image is
+// downloaded first, keeping the bytes already read
+TEST_F(OnlineImageDownloadEnd, JpegHeadersLargerThanTheBufferDownloadTheWholeImage) {
+  auto image = this->make_image_(runtime_image::JPEG, 256);
+  auto container = std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)),
+                                                   sizeof(JPEG_48X40), false);
+  this->start_(*image, container);
+
+  for (int i = 0; i < 100 && this->finished_ + this->errors_ == 0; i++) {
+    image->loop();
+    container->deliver(256);
+  }
+
+  ASSERT_EQ(this->finished_, 1);
+  EXPECT_EQ(this->errors_, 0);
+  EXPECT_EQ(container->get_bytes_read(), sizeof(JPEG_48X40));
+  EXPECT_EQ(image_pixels(*image), reference_jpeg_pixels());
+}
+
+// The pass that opens the image does not decode any of it
+TEST_F(OnlineImageDownloadEnd, JpegOpensInAPassOfItsOwn) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  auto container = std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)),
+                                                   sizeof(JPEG_48X40), false);
+  this->start_(*image, container);
+
+  image->loop();
+  EXPECT_EQ(this->finished_ + this->errors_, 0);
+  for (int i = 0; i < 100 && this->finished_ + this->errors_ == 0; i++)
+    image->loop();
+  EXPECT_EQ(this->finished_, 1);
+}
+
+// A progressive JPEG is refused while it downloads, without blaming the buffer size
+TEST_F(OnlineImageDownloadEnd, JpegProgressiveReportsError) {
+  auto image = this->make_image_(runtime_image::JPEG, 256);
+  std::vector<uint8_t> body(JPEG_PROGRESSIVE, JPEG_PROGRESSIVE + sizeof(JPEG_PROGRESSIVE));
+  auto container = std::make_shared<FakeContainer>(body, 256, false);
+  this->start_(*image, container);
+
+  for (int i = 0; i < 10 && this->finished_ + this->errors_ == 0; i++)
+    image->loop();
+
+  EXPECT_EQ(this->errors_, 1);
+  EXPECT_EQ(this->finished_, 0);
+}
+
+// on_download_started fires once the server has accepted the request, before the first progress report, and not
+// for a response that has no image to download
+TEST_F(OnlineImageDownloadEnd, StartedFiresOnlyWhenTheDownloadBegins) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  std::vector<std::string> events;
+  image->add_on_download_started_callback([&events]() { events.emplace_back("started"); });
+  image->add_on_progress_callback([&events](float, size_t) { events.emplace_back("progress"); });
+  this->start_(*image,
+               std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)),
+                                               sizeof(JPEG_48X40), false));
+  ASSERT_GE(events.size(), 2u);
+  EXPECT_EQ(events[0], "started");
+  EXPECT_EQ(events[1], "progress");
+  for (int i = 0; i < 100 && this->finished_ + this->errors_ == 0; i++)
+    image->loop();
+  EXPECT_EQ(std::count(events.begin(), events.end(), std::string("started")), 1);
+
+  for (int status : {304, 404}) {
+    events.clear();
+    auto container = std::make_shared<FakeContainer>(std::vector<uint8_t>{}, 0, false);
+    container->status_code = status;
+    this->http_.next = container;
+    image->update();
+    EXPECT_TRUE(events.empty()) << "HTTP " << status;
+  }
+}
+
+// Progress starts at 0, is reported at most every 100 ms, and always reaches 100%
+TEST_F(OnlineImageDownloadEnd, ProgressIsReportedAsTheImageDownloads) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  std::vector<float> reports;
+  image->add_on_progress_callback([&reports](float progress, size_t) { reports.push_back(progress); });
+  auto container =
+      std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)), 100, false);
+  uint32_t now = 1000;
+  set_loop_time(now);
+  this->start_(*image, container);
+  ASSERT_EQ(reports.size(), 1u);
+  EXPECT_EQ(reports[0], 0.0f);
+
+  int passes = 0;
+  for (; passes < 1000 && this->finished_ + this->errors_ == 0; passes++) {
+    now += 50;
+    set_loop_time(now);
+    container->deliver(100);
+    image->loop();
+  }
+
+  ASSERT_EQ(this->finished_, 1);
+  EXPECT_EQ(reports.back(), 100.0f);
+  EXPECT_TRUE(std::is_sorted(reports.begin(), reports.end()));
+  // A report every 100 ms of a 50 ms loop, plus the start and the end
+  EXPECT_LE(reports.size(), static_cast<size_t>(passes / 2 + 2));
+  EXPECT_GT(reports.size(), 3u);
+}
+
+// Without a Content-Length the percentage is unknown, but the bytes read are still reported
+TEST_F(OnlineImageDownloadEnd, ProgressOfAChunkedDownloadHasNoPercentage) {
+  auto image = this->make_image_(runtime_image::PNG);
+  std::vector<std::pair<float, size_t>> reports;
+  image->add_on_progress_callback(
+      [&reports](float progress, size_t bytes_read) { reports.emplace_back(progress, bytes_read); });
+  auto container =
+      std::make_shared<FakeContainer>(std::vector<uint8_t>(PNG_1X1.begin(), PNG_1X1.end()), PNG_1X1.size(), true);
+  set_loop_time(1000);
+  this->start_(*image, container);
+  set_loop_time(2000);
+  for (int i = 0; i < 10 && this->finished_ + this->errors_ == 0; i++)
+    image->loop();
+
+  ASSERT_GE(reports.size(), 2u);
+  EXPECT_TRUE(std::isnan(reports.back().first));
+  EXPECT_EQ(reports.back().second, PNG_1X1.size());
+}
+
+// Scan data that cannot be decoded fails the download part way through
+TEST_F(OnlineImageDownloadEnd, JpegDecodeErrorFailsTheDownload) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  std::vector<uint8_t> body(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40));
+  std::fill(body.begin() + 700, body.end() - 2, 0xFE);
+  auto container = std::make_shared<FakeContainer>(body, 1024, false);
+  this->start_(*image, container);
+
+  for (int i = 0; i < 100 && this->finished_ + this->errors_ == 0; i++) {
+    image->loop();
+    container->deliver(256);
+  }
+
+  EXPECT_EQ(this->errors_, 1);
+  EXPECT_EQ(this->finished_, 0);
+}
+
+// A read that fails part way through the download ends it with an error
+TEST_F(OnlineImageDownloadEnd, JpegReadErrorFailsTheDownload) {
+  auto image = this->make_image_(runtime_image::JPEG, 1024);
+  auto container =
+      std::make_shared<FakeContainer>(std::vector<uint8_t>(JPEG_48X40, JPEG_48X40 + sizeof(JPEG_48X40)), 1024, false);
+  this->start_(*image, container);
+  for (int i = 0; i < 5; i++)
+    image->loop();
+  ASSERT_EQ(this->errors_, 0);
+
+  container->fail_reads();
+  image->loop();
+  EXPECT_EQ(this->errors_, 1);
+  EXPECT_EQ(this->finished_, 0);
+}
+
+TEST(DownloadBufferGrow, KeepsTheUnreadData) {
+  DownloadBuffer buffer(16);
+  std::memcpy(buffer.append(), "abcdef", 6);
+  buffer.write(6);
+  buffer.read(2);
+
+  ASSERT_TRUE(buffer.grow(64));
+  EXPECT_EQ(buffer.size(), 64u);
+  ASSERT_EQ(buffer.unread(), 4u);
+  EXPECT_EQ(std::memcmp(buffer.data(), "cdef", 4), 0);
+
+  // A failed allocation leaves the buffer as it was
+  EXPECT_FALSE(buffer.grow(SIZE_MAX / 2));
+  EXPECT_EQ(buffer.size(), 64u);
+  EXPECT_EQ(std::memcmp(buffer.data(), "cdef", 4), 0);
+  // Growing to a smaller size changes nothing
+  EXPECT_TRUE(buffer.grow(8));
+  EXPECT_EQ(buffer.size(), 64u);
+}
+
 }  // namespace esphome::online_image::testing

tests/components/runtime_image/test_decoder_reuse.cpp

@@ -4,9 +4,11 @@
 #include <algorithm>
 #include <array>
 #include <cstring>
+#include <utility>
 #include <vector>
 
 #include "esphome/components/runtime_image/image_decoder.h"
+#include "esphome/components/runtime_image/jpeg_decoder.h"
 #include "esphome/components/runtime_image/runtime_image.h"
 
 namespace esphome::runtime_image::testing {
@@ -362,6 +364,23 @@ static std::vector<uint8_t> pixel_bytes(TestableRuntimeImage &img) {
   return std::vector<uint8_t>(start, start + img.get_width_stride() * img.get_height());
 }
 
+// Shrinking a PNG keeps the first source pixel of each span, as the JPEG path does: the even rows and columns
+TEST(RuntimeImageDecoder, ShrunkPngKeepsTheFirstPixelOfEachSpan) {
+  TestableRuntimeImage img(PNG, image::IMAGE_TYPE_RGB, false, 2, 2);
+  ASSERT_TRUE(decode_all(img, PNG_RGB, sizeof(PNG_RGB), PNG));
+  ASSERT_EQ(img.get_width(), 2);
+  ASSERT_EQ(img.get_height(), 2);
+  for (int row = 0; row < 2; row++) {
+    for (int col = 0; col < 2; col++) {
+      const Color pixel = img.get_pixel(col, row);
+      const uint8_t *expected = PNG_RGB_EXPECTED[row * 2][col * 2];
+      EXPECT_EQ(pixel.r, expected[0]) << col << "," << row;
+      EXPECT_EQ(pixel.g, expected[1]) << col << "," << row;
+      EXPECT_EQ(pixel.b, expected[2]) << col << "," << row;
+    }
+  }
+}
+
 TEST(RuntimeImageDecoder, JpegDecoderStaysWarmAcrossDecodes) {
   TestableRuntimeImage img(JPEG);
 
@@ -377,6 +396,12 @@ TEST(RuntimeImageDecoder, JpegDecoderStaysWarmAcrossDecodes) {
   EXPECT_EQ(pixel_bytes(img), first_pixels) << "reused decoder must reproduce identical pixels";
 }
 
+// The RGB565 word at (x, y) of a decoded image, in its own byte order
+static uint16_t rgb565_word(const TestableRuntimeImage &img, int x, int y) {
+  const uint8_t *p = img.get_data_start() + (y * img.get_width() + x) * 2;
+  return p[0] | (p[1] << 8);
+}
+
 // JPEGDEC's colour conversion differs by one step between its SIMD and scalar builds, so each
 // channel is checked within one step; the byte order is still exact
 static void expect_rgb565_near(uint16_t actual, uint16_t expected, const char *order, size_t pixel) {
@@ -386,16 +411,12 @@ static void expect_rgb565_near(uint16_t actual, uint16_t expected, const char *o
 }
 
 TEST(RuntimeImageDecoder, JpegDecodesDirectlyToScaledRgb565WithBothByteOrders) {
-  // Halving the 8x8 gradient keeps its even rows and columns. The words are JPEGDEC's output for those
-  // pixels, red in the top five bits: a decode of the fixture with PIL gives (51, 7, 30) for source
-  // pixel (2, 0), which is word 0x3803 here.
-  static const uint16_t EXPECTED[4 * 4] = {
-      0x0000, 0x3803, 0x8008, 0xB80B, 0x0203, 0x3A07, 0x81EC, 0xBA0F,
-      0x03E7, 0x3C0B, 0x83F0, 0xBC13, 0x05EC, 0x3E0F, 0x85F4, 0xBE17,
-  };
+  // Halving the 8x8 gradient makes JPEGDEC decode it at half size, which averages each 2x2 block of pixels
+  TestableRuntimeImage full(JPEG, image::IMAGE_TYPE_RGB565, false, 8, 8);
   TestableRuntimeImage rgb565_little_endian(JPEG, image::IMAGE_TYPE_RGB565, false, 4, 4);
   TestableRuntimeImage rgb565_big_endian(JPEG, image::IMAGE_TYPE_RGB565, true, 4, 4);
 
+  ASSERT_TRUE(decode_all(full, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
   ASSERT_TRUE(decode_all(rgb565_little_endian, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
   ASSERT_TRUE(decode_all(rgb565_big_endian, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
   ASSERT_EQ(rgb565_little_endian.get_width(), 4);
@@ -405,9 +426,53 @@ TEST(RuntimeImageDecoder, JpegDecodesDirectlyToScaledRgb565WithBothByteOrders) {
 
   const uint8_t *little = rgb565_little_endian.get_data_start();
   const uint8_t *big = rgb565_big_endian.get_data_start();
-  for (size_t i = 0; i < 4 * 4; i++) {
-    expect_rgb565_near(little[i * 2] | (little[i * 2 + 1] << 8), EXPECTED[i], "little-endian", i);
-    expect_rgb565_near((big[i * 2] << 8) | big[i * 2 + 1], EXPECTED[i], "big-endian", i);
+  for (int row = 0; row < 4; row++) {
+    for (int col = 0; col < 4; col++) {
+      int red = 0;
+      int green = 0;
+      int blue = 0;
+      for (int dy = 0; dy < 2; dy++) {
+        for (int dx = 0; dx < 2; dx++) {
+          const uint16_t word = rgb565_word(full, col * 2 + dx, row * 2 + dy);
+          red += word >> 11;
+          green += (word >> 5) & 0x3F;
+          blue += word & 0x1F;
+        }
+      }
+      const uint16_t expected = ((red + 2) / 4) << 11 | ((green + 2) / 4) << 5 | (blue + 2) / 4;
+      const size_t i = row * 4 + col;
+      expect_rgb565_near(little[i * 2] | (little[i * 2 + 1] << 8), expected, "little-endian", i);
+      expect_rgb565_near((big[i * 2] << 8) | big[i * 2 + 1], expected, "big-endian", i);
+    }
+  }
+}
+
+// The generic draw() path gets JPEGDEC's half size RGB8888 output, so it too averages each 2x2 block of pixels
+TEST(RuntimeImageDecoder, JpegDecodesToScaledRgb) {
+  TestableRuntimeImage full(JPEG, image::IMAGE_TYPE_RGB, false, 8, 8);
+  TestableRuntimeImage half(JPEG, image::IMAGE_TYPE_RGB, false, 4, 4);
+  ASSERT_TRUE(decode_all(full, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
+  ASSERT_TRUE(decode_all(half, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
+  ASSERT_EQ(static_cast<JpegDecoder *>(half.decoder())->get_scale(), 2);
+
+  for (int row = 0; row < 4; row++) {
+    for (int col = 0; col < 4; col++) {
+      int red = 0;
+      int green = 0;
+      int blue = 0;
+      for (int dy = 0; dy < 2; dy++) {
+        for (int dx = 0; dx < 2; dx++) {
+          const Color pixel = full.get_pixel(col * 2 + dx, row * 2 + dy);
+          red += pixel.r;
+          green += pixel.g;
+          blue += pixel.b;
+        }
+      }
+      const Color pixel = half.get_pixel(col, row);
+      EXPECT_NEAR(pixel.r, (red + 2) / 4, 8) << "pixel " << col << "," << row << " red";
+      EXPECT_NEAR(pixel.g, (green + 2) / 4, 8) << "pixel " << col << "," << row << " green";
+      EXPECT_NEAR(pixel.b, (blue + 2) / 4, 8) << "pixel " << col << "," << row << " blue";
+    }
   }
 }
 
@@ -415,10 +480,15 @@ TEST(RuntimeImageDecoder, JpegDecodesDirectlyToScaledRgb565WithBothByteOrders) {
 // prepare_rgb565_scaling_ rounds: source n covers targets ceil(n * target / source) up to the next start
 static uint16_t scaled_boundary(int n, int source, int target) { return (n * target + source - 1) / source; }
 
-// The RGB565 word at (x, y) of a decoded image, in its own byte order
-static uint16_t rgb565_word(const TestableRuntimeImage &img, int x, int y) {
-  const uint8_t *p = img.get_data_start() + (y * img.get_width() + x) * 2;
-  return p[0] | (p[1] << 8);
+// JPEGDEC decodes at the smallest of full, 1/2, 1/4 and 1/8 size that still covers the buffer
+TEST(RuntimeImageDecoder, JpegDecodesAtTheSmallestSizeThatCoversTheBuffer) {
+  for (auto [size, scale] :
+       {std::pair{8, 1}, std::pair{5, 1}, std::pair{4, 2}, std::pair{3, 2}, std::pair{2, 4}, std::pair{1, 8}}) {
+    TestableRuntimeImage img(JPEG, image::IMAGE_TYPE_RGB565, false, size, size);
+    ASSERT_TRUE(decode_all(img, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
+    EXPECT_EQ(img.get_width(), size);
+    EXPECT_EQ(static_cast<JpegDecoder *>(img.decoder())->get_scale(), scale) << size << "x" << size;
+  }
 }
 
 // Every scaled direct decode must equal the unscaled one sampled through the boundary table,
@@ -427,7 +497,8 @@ TEST(RuntimeImageDecoder, JpegDirectRgb565ScalesBySourcePixelSpans) {
   TestableRuntimeImage full(JPEG, image::IMAGE_TYPE_RGB565, false, 8, 8);
   ASSERT_TRUE(decode_all(full, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
 
-  for (int size : {4, 6, 16}) {
+  // Sizes JPEGDEC cannot reach by scaling, so the full size decode is spread over the buffer
+  for (int size : {5, 6, 16}) {
     TestableRuntimeImage scaled(JPEG, image::IMAGE_TYPE_RGB565, false, size, size);
     ASSERT_TRUE(decode_all(scaled, JPEG_GRADIENT, sizeof(JPEG_GRADIENT)));
     ASSERT_EQ(scaled.get_width(), size);

tests/components/runtime_image/test_grayscale_pixel.cpp

@@ -0,0 +1,35 @@
+#include <gtest/gtest.h>
+
+#include <cstdint>
+#include <cstdlib>
+
+#include "esphome/components/runtime_image/runtime_image.h"
+
+namespace esphome::runtime_image::testing {
+
+class GrayscaleImage : public RuntimeImage {
+ public:
+  GrayscaleImage() : RuntimeImage(BMP, image::IMAGE_TYPE_GRAYSCALE, image::TRANSPARENCY_OPAQUE) {}
+  uint8_t pixel(int x) const { return this->buffer_[x]; }
+};
+
+// The integer weights stay within one step of the floating point formula they replace, and keep white at 255
+TEST(GrayscalePixel, MatchesTheFloatingPointWeights) {
+  GrayscaleImage img;
+  ASSERT_GT(img.resize(256, 1), 0);
+  for (int r = 0; r < 256; r += 5) {
+    for (int g = 0; g < 256; g += 5) {
+      for (int b = 0; b < 256; b += 5) {
+        img.draw_pixel(0, 0, Color(r, g, b));
+        const int expected = static_cast<int>(0.2125 * r + 0.7154 * g + 0.0721 * b);
+        ASSERT_LE(std::abs(img.pixel(0) - expected), 1) << "r=" << r << " g=" << g << " b=" << b;
+      }
+    }
+  }
+  img.draw_pixel(1, 0, Color(255, 255, 255));
+  EXPECT_EQ(img.pixel(1), 255);
+  img.draw_pixel(2, 0, Color(0, 0, 0));
+  EXPECT_EQ(img.pixel(2), 0);
+}
+
+}  // namespace esphome::runtime_image::testing

tests/components/runtime_image/test_jpeg_grayscale.cpp

@@ -0,0 +1,83 @@
+#include <gtest/gtest.h>
+
+#include <cstdlib>
+#include <vector>
+
+#include "esphome/components/runtime_image/runtime_image.h"
+
+#ifdef USE_RUNTIME_IMAGE_JPEG
+
+namespace esphome::runtime_image::testing {
+
+// 16x8 grayscale JPEG (quality 95) of a smooth gradient, from 60 at the top left to 185 at the bottom right
+static const uint8_t JPEG_GRAY[] = {
+    0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00,
+    0x00, 0xFF, 0xDB, 0x00, 0x43, 0x00, 0x02, 0x01, 0x01, 0x01, 0x01, 0x01, 0x02, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02,
+    0x02, 0x02, 0x04, 0x03, 0x02, 0x02, 0x02, 0x02, 0x05, 0x04, 0x04, 0x03, 0x04, 0x06, 0x05, 0x06, 0x06, 0x06, 0x05,
+    0x06, 0x06, 0x06, 0x07, 0x09, 0x08, 0x06, 0x07, 0x09, 0x07, 0x06, 0x06, 0x08, 0x0B, 0x08, 0x09, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x06, 0x08, 0x0B, 0x0C, 0x0B, 0x0A, 0x0C, 0x09, 0x0A, 0x0A, 0x0A, 0xFF, 0xC0, 0x00, 0x0B, 0x08, 0x00,
+    0x08, 0x00, 0x10, 0x01, 0x01, 0x11, 0x00, 0xFF, 0xC4, 0x00, 0x1F, 0x00, 0x00, 0x01, 0x05, 0x01, 0x01, 0x01, 0x01,
+    0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
+    0x0A, 0x0B, 0xFF, 0xC4, 0x00, 0xB5, 0x10, 0x00, 0x02, 0x01, 0x03, 0x03, 0x02, 0x04, 0x03, 0x05, 0x05, 0x04, 0x04,
+    0x00, 0x00, 0x01, 0x7D, 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12, 0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61,
+    0x07, 0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xA1, 0x08, 0x23, 0x42, 0xB1, 0xC1, 0x15, 0x52, 0xD1, 0xF0, 0x24, 0x33,
+    0x62, 0x72, 0x82, 0x09, 0x0A, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x34, 0x35, 0x36,
+    0x37, 0x38, 0x39, 0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
+    0x5A, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x83, 0x84,
+    0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5,
+    0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6,
+    0xC7, 0xC8, 0xC9, 0xCA, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6,
+    0xE7, 0xE8, 0xE9, 0xEA, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFF, 0xDA, 0x00, 0x08, 0x01,
+    0x01, 0x00, 0x00, 0x3F, 0x00, 0xF0, 0x9F, 0x82, 0x5F, 0x09, 0x3F, 0xD4, 0xFF, 0x00, 0xA2, 0xFA, 0x76, 0xAF, 0xB0,
+    0x3E, 0x09, 0x7C, 0x24, 0xFF, 0x00, 0x53, 0xFE, 0x8B, 0xE9, 0xDA, 0xBF, 0xFF, 0xD9,
+};
+
+// The pixels Pillow decodes from it
+static const uint8_t JPEG_GRAY_PIXELS[8 * 16] = {
+    60,  66,  72,  78,  84,  90,  96,  102, 108, 114, 120, 126, 132, 138, 144, 150, 65,  71,  77,  83,  89,  95,
+    101, 107, 113, 119, 125, 131, 137, 143, 149, 155, 70,  76,  82,  88,  94,  100, 106, 112, 118, 124, 130, 136,
+    142, 148, 154, 160, 75,  81,  87,  93,  99,  105, 111, 117, 123, 129, 135, 141, 147, 153, 159, 165, 80,  86,
+    92,  98,  104, 110, 116, 122, 128, 134, 140, 146, 152, 158, 164, 170, 85,  91,  97,  103, 109, 115, 121, 127,
+    133, 139, 145, 151, 157, 163, 169, 175, 90,  96,  102, 108, 114, 120, 126, 132, 138, 144, 150, 156, 162, 168,
+    174, 180, 95,  101, 107, 113, 119, 125, 131, 137, 143, 149, 155, 161, 167, 173, 179, 185,
+};
+
+// JPEGDEC's faster inverse DCT is up to 4 steps from Pillow's on this image; the garbled output was off by hundreds
+static constexpr int TOLERANCE = 5;
+
+static bool decode(RuntimeImage &img) {
+  std::vector<uint8_t> data(JPEG_GRAY, JPEG_GRAY + sizeof(JPEG_GRAY));
+  if (!img.begin_decode(data.size()))
+    return false;
+  if (img.feed_data(data.data(), data.size()) != static_cast<int>(data.size()))
+    return false;
+  return img.end_decode();
+}
+
+// A grayscale JPEG decoded for a colour image goes through JPEGDEC's RGB8888 output, which used to be garbled
+TEST(JpegGrayscale, DecodesToRgb) {
+  RuntimeImage img(JPEG, image::IMAGE_TYPE_RGB, image::TRANSPARENCY_ALPHA_CHANNEL);
+  ASSERT_TRUE(decode(img));
+  ASSERT_EQ(img.get_width(), 16);
+  ASSERT_EQ(img.get_height(), 8);
+  const uint8_t *data = img.get_data_start();
+  for (int i = 0; i < 16 * 8; i++) {
+    const uint8_t *pixel = data + i * 4;  // blue, green, red, alpha
+    EXPECT_NEAR(pixel[0], JPEG_GRAY_PIXELS[i], TOLERANCE) << "blue of pixel " << i;
+    EXPECT_NEAR(pixel[1], JPEG_GRAY_PIXELS[i], TOLERANCE) << "green of pixel " << i;
+    EXPECT_NEAR(pixel[2], JPEG_GRAY_PIXELS[i], TOLERANCE) << "red of pixel " << i;
+    EXPECT_EQ(pixel[3], 255) << "alpha of pixel " << i;
+  }
+}
+
+TEST(JpegGrayscale, DecodesToGrayscale) {
+  RuntimeImage img(JPEG, image::IMAGE_TYPE_GRAYSCALE, image::TRANSPARENCY_OPAQUE);
+  ASSERT_TRUE(decode(img));
+  const uint8_t *data = img.get_data_start();
+  for (int i = 0; i < 16 * 8; i++)
+    EXPECT_NEAR(data[i], JPEG_GRAY_PIXELS[i], TOLERANCE) << "pixel " << i;
+}
+
+}  // namespace esphome::runtime_image::testing
+
+#endif  // USE_RUNTIME_IMAGE_JPEG

tests/components/runtime_image/test_jpeg_source.cpp

@@ -0,0 +1,453 @@
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <cstring>
+#include <vector>
+
+#include "esphome/components/runtime_image/image_decoder.h"
+#include "esphome/components/runtime_image/jpeg_decoder.h"
+#include "esphome/components/runtime_image/runtime_image.h"
+
+#ifdef USE_RUNTIME_IMAGE_JPEG
+
+namespace esphome::runtime_image::testing {
+
+// 48x40 4:2:0 JPEG of a noisy gradient (quality 95): three rows of 16 pixel MCUs, so a stepped decode takes
+// three steps. At 2344 bytes it is larger than JPEGDEC's 2048 byte read buffer, so the source is read again
+// part way through the image.
+static const uint8_t JPEG_ROWS[] = {
+    0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00,
+    0x00, 0xFF, 0xDB, 0x00, 0x43, 0x00, 0x02, 0x01, 0x01, 0x01, 0x01, 0x01, 0x02, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02,
+    0x02, 0x02, 0x04, 0x03, 0x02, 0x02, 0x02, 0x02, 0x05, 0x04, 0x04, 0x03, 0x04, 0x06, 0x05, 0x06, 0x06, 0x06, 0x05,
+    0x06, 0x06, 0x06, 0x07, 0x09, 0x08, 0x06, 0x07, 0x09, 0x07, 0x06, 0x06, 0x08, 0x0B, 0x08, 0x09, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x06, 0x08, 0x0B, 0x0C, 0x0B, 0x0A, 0x0C, 0x09, 0x0A, 0x0A, 0x0A, 0xFF, 0xDB, 0x00, 0x43, 0x01, 0x02,
+    0x02, 0x02, 0x02, 0x02, 0x02, 0x05, 0x03, 0x03, 0x05, 0x0A, 0x07, 0x06, 0x07, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
+    0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0xFF, 0xC0, 0x00, 0x11, 0x08, 0x00, 0x28, 0x00, 0x30, 0x03, 0x01, 0x22, 0x00,
+    0x02, 0x11, 0x01, 0x03, 0x11, 0x01, 0xFF, 0xC4, 0x00, 0x1F, 0x00, 0x00, 0x01, 0x05, 0x01, 0x01, 0x01, 0x01, 0x01,
+    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A,
+    0x0B, 0xFF, 0xC4, 0x00, 0xB5, 0x10, 0x00, 0x02, 0x01, 0x03, 0x03, 0x02, 0x04, 0x03, 0x05, 0x05, 0x04, 0x04, 0x00,
+    0x00, 0x01, 0x7D, 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12, 0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
+    0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xA1, 0x08, 0x23, 0x42, 0xB1, 0xC1, 0x15, 0x52, 0xD1, 0xF0, 0x24, 0x33, 0x62,
+    0x72, 0x82, 0x09, 0x0A, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x34, 0x35, 0x36, 0x37,
+    0x38, 0x39, 0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A,
+    0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x83, 0x84, 0x85,
+    0x86, 0x87, 0x88, 0x89, 0x8A, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6,
+    0xA7, 0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7,
+    0xC8, 0xC9, 0xCA, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7,
+    0xE8, 0xE9, 0xEA, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFF, 0xC4, 0x00, 0x1F, 0x01, 0x00,
+    0x03, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03,
+    0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0xFF, 0xC4, 0x00, 0xB5, 0x11, 0x00, 0x02, 0x01, 0x02, 0x04, 0x04,
+    0x03, 0x04, 0x07, 0x05, 0x04, 0x04, 0x00, 0x01, 0x02, 0x77, 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21, 0x31,
+    0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71, 0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91, 0xA1, 0xB1, 0xC1, 0x09,
+    0x23, 0x33, 0x52, 0xF0, 0x15, 0x62, 0x72, 0xD1, 0x0A, 0x16, 0x24, 0x34, 0xE1, 0x25, 0xF1, 0x17, 0x18, 0x19, 0x1A,
+    0x26, 0x27, 0x28, 0x29, 0x2A, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A,
+    0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5A, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x73, 0x74, 0x75,
+    0x76, 0x77, 0x78, 0x79, 0x7A, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x92, 0x93, 0x94, 0x95, 0x96,
+    0x97, 0x98, 0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7,
+    0xB8, 0xB9, 0xBA, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8,
+    0xD9, 0xDA, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9,
+    0xFA, 0xFF, 0xDA, 0x00, 0x0C, 0x03, 0x01, 0x00, 0x02, 0x11, 0x03, 0x11, 0x00, 0x3F, 0x00, 0xFC, 0xAA, 0xB8, 0xB7,
+    0xD3, 0xB5, 0xD8, 0x1E, 0xD6, 0xD1, 0xA5, 0x5B, 0x4B, 0x46, 0x10, 0xC1, 0x06, 0xA1, 0x29, 0x69, 0x25, 0xB7, 0xC2,
+    0xC6, 0x0C, 0x71, 0x26, 0x5E, 0x50, 0x15, 0x5D, 0xB6, 0x9C, 0x9E, 0x00, 0xC1, 0x67, 0x67, 0x4D, 0xCF, 0x84, 0xF7,
+    0x57, 0xA6, 0xDA, 0x08, 0x52, 0xF5, 0xE5, 0xBA, 0xB8, 0x7B, 0x5B, 0x68, 0xEE, 0x2F, 0x66, 0x89, 0xB7, 0xB7, 0x9B,
+    0xE5, 0x9C, 0x23, 0xAA, 0xFE, 0xF7, 0x68, 0x11, 0x9E, 0x5D, 0x18, 0x12, 0x48, 0x56, 0x5C, 0x9F, 0x57, 0xB6, 0xF8,
+    0x33, 0xF0, 0xE2, 0x5B, 0xFB, 0xCF, 0xF4, 0x51, 0x0C, 0xC6, 0x64, 0x30, 0x49, 0x71, 0x7C, 0xE2, 0x16, 0x90, 0x2E,
+    0xF4, 0x72, 0xEA, 0xE0, 0x34, 0x81, 0x77, 0x93, 0x9C, 0x07, 0xC2, 0x93, 0xB9, 0x61, 0xC0, 0xD3, 0xF0, 0x17, 0xC1,
+    0xBF, 0x03, 0xCD, 0xE1, 0xAD, 0x42, 0x3F, 0x0A, 0xD8, 0xC7, 0x2D, 0xAC, 0x36, 0xCB, 0xF6, 0x79, 0x22, 0x69, 0x84,
+    0xC4, 0x93, 0x29, 0x2A, 0x89, 0xB9, 0x00, 0x50, 0x62, 0x7C, 0xFF, 0x00, 0x16, 0xD9, 0x65, 0x00, 0x16, 0x65, 0x07,
+    0xFA, 0x5B, 0x36, 0xE2, 0xAC, 0xBF, 0x2D, 0x55, 0x79, 0x29, 0xB5, 0x26, 0x9B, 0xA9, 0x18, 0xB5, 0x15, 0x36, 0x9B,
+    0x53, 0xD1, 0xCA, 0x10, 0x93, 0x69, 0xB6, 0x94, 0x27, 0x16, 0xAF, 0x19, 0x29, 0xB8, 0xBB, 0x3F, 0x9A, 0xE1, 0x1E,
+    0x2A, 0xCB, 0x9E, 0x79, 0x4A, 0x92, 0x84, 0xDA, 0xD6, 0xED, 0xA4, 0xED, 0x7A, 0x72, 0xB5, 0xAC, 0xF6, 0xEB, 0xAD,
+    0xD5, 0x97, 0x91, 0xC9, 0x4D, 0xA4, 0xE9, 0xD7, 0x56, 0x45, 0x66, 0xD3, 0x9D, 0x85, 0xB1, 0x86, 0x59, 0x7E, 0xD9,
+    0x7E, 0xA0, 0xE0, 0xA8, 0x02, 0x17, 0x02, 0x3C, 0x36, 0x59, 0x18, 0xE2, 0x42, 0x1D, 0x40, 0x56, 0x0A, 0x77, 0x30,
+    0xAE, 0xFA, 0x56, 0xD4, 0xA4, 0x8A, 0xD9, 0xAD, 0xD6, 0x38, 0x1D, 0x7F, 0x77, 0x77, 0x1C, 0xB2, 0x4C, 0x22, 0x8C,
+    0x2B, 0xF3, 0x14, 0x64, 0x45, 0x85, 0x52, 0x47, 0x92, 0x7E, 0xF2, 0x0F, 0x34, 0x1D, 0xBC, 0x56, 0xDE, 0x85, 0xF0,
+    0x4B, 0xE1, 0x0A, 0xE9, 0xB0, 0xDB, 0x2D, 0x8C, 0x4C, 0xCD, 0x74, 0xF1, 0x42, 0x96, 0x93, 0xCF, 0xF6, 0x54, 0x0C,
+    0xB3, 0x44, 0x03, 0xAA, 0x6C, 0x49, 0x10, 0x87, 0x00, 0x88, 0xC2, 0xEE, 0x66, 0x6F, 0x9B, 0xAB, 0x57, 0xA4, 0x68,
+    0xDF, 0x0A, 0x3E, 0x1B, 0xDA, 0xE9, 0xDF, 0xD9, 0x96, 0xFE, 0x03, 0xB2, 0x8E, 0xD9, 0x8A, 0xDD, 0xC1, 0x77, 0x14,
+    0x97, 0x50, 0x2E, 0xE3, 0x20, 0x62, 0xA0, 0x33, 0x0C, 0xC6, 0x58, 0x48, 0x36, 0x6D, 0xC1, 0x20, 0xA2, 0x2B, 0x00,
+    0xB5, 0xF1, 0x99, 0xCF, 0x19, 0x65, 0x79, 0xAD, 0x0C, 0x3C, 0x2B, 0x61, 0xF9, 0x28, 0xD6, 0x52, 0x97, 0x35, 0x95,
+    0xD4, 0x61, 0x28, 0x5B, 0x99, 0xB8, 0xA9, 0xA9, 0x47, 0xD9, 0x3A, 0x69, 0xA9, 0xC6, 0x51, 0x52, 0x6A, 0x0D, 0x4A,
+    0x74, 0xA9, 0xC3, 0xFA, 0x7F, 0xC3, 0xFE, 0x25, 0xC1, 0x4E, 0xAE, 0x26, 0x2E, 0x13, 0x71, 0x5C, 0x8D, 0xFB, 0xB1,
+    0xD6, 0xEA, 0x6F, 0xF9, 0xAF, 0xBE, 0xB7, 0x4B, 0x55, 0x1D, 0x75, 0x4C, 0xF3, 0xDF, 0x05, 0xD9, 0xF8, 0x7B, 0xC3,
+    0xBA, 0xB5, 0xF1, 0xBC, 0x8D, 0x63, 0xDF, 0x1C, 0x32, 0x88, 0x1A, 0xF3, 0x74, 0x73, 0x89, 0x15, 0xC4, 0x8A, 0x25,
+    0x66, 0xDC, 0xAA, 0x98, 0x60, 0x06, 0x7F, 0xBD, 0xF2, 0x81, 0xF3, 0x36, 0xFE, 0x9D, 0xAF, 0x78, 0x8F, 0x54, 0xD3,
+    0xAD, 0xA6, 0x9E, 0xC5, 0xE5, 0x9C, 0x96, 0xDC, 0xB7, 0xE8, 0x84, 0x47, 0xFB, 0xB4, 0x54, 0x42, 0x0F, 0x03, 0xF8,
+    0xD7, 0xE5, 0x39, 0x60, 0xF8, 0x04, 0x79, 0x7B, 0xE3, 0xF4, 0x9F, 0x85, 0x5F, 0x08, 0xBE, 0x0D, 0x2C, 0x57, 0xCE,
+    0x6C, 0xA5, 0x2B, 0xA8, 0x08, 0x20, 0x82, 0x04, 0xB9, 0xB8, 0x82, 0x43, 0x28, 0x72, 0x55, 0xD5, 0x83, 0xB9, 0x05,
+    0xC2, 0x44, 0x55, 0x77, 0x8C, 0xFC, 0xEC, 0xD8, 0xCB, 0xE7, 0xBE, 0x9B, 0xE0, 0x5F, 0xC3, 0x9D, 0x32, 0xD4, 0x45,
+    0x26, 0x8B, 0x2C, 0x93, 0xC0, 0xF3, 0x95, 0x49, 0xEE, 0x2E, 0x0C, 0x26, 0x26, 0x31, 0xC9, 0xF3, 0xED, 0x95, 0x96,
+    0x32, 0xEC, 0x10, 0xE1, 0xB8, 0x60, 0x3A, 0x90, 0x1B, 0x3F, 0x9E, 0x66, 0x58, 0xFC, 0x14, 0x31, 0x15, 0xFD, 0x9C,
+    0x79, 0x57, 0x3A, 0x92, 0x84, 0x1C, 0x3D, 0xC9, 0xCD, 0x27, 0x6D, 0x12, 0xE5, 0xE7, 0xA6, 0xD5, 0x4D, 0x64, 0x93,
+    0xD1, 0x45, 0xC6, 0xAD, 0xE7, 0x2F, 0xE9, 0xEE, 0x17, 0xE3, 0x0C, 0x0A, 0xE1, 0x9C, 0x37, 0x34, 0x67, 0x2B, 0x73,
+    0x2B, 0xB4, 0xBA, 0x49, 0xF4, 0x72, 0x57, 0x51, 0xDD, 0x24, 0x9B, 0x5A, 0x36, 0x9A, 0x49, 0x1E, 0x15, 0xA7, 0x7E,
+    0xCE, 0xF6, 0x89, 0x6A, 0x96, 0x43, 0x55, 0xB5, 0xB3, 0xB6, 0xB8, 0x96, 0x2B, 0x9B, 0x78, 0xA0, 0xB4, 0x9E, 0xE5,
+    0x61, 0x90, 0xE0, 0xC2, 0xEC, 0x61, 0x91, 0x47, 0xCC, 0xDB, 0xF1, 0x80, 0xC0, 0x98, 0xD4, 0xE5, 0xDC, 0x64, 0xEC,
+    0x7C, 0x29, 0xFD, 0x98, 0x6C, 0xAF, 0xEC, 0xF5, 0x76, 0xB7, 0xF1, 0x36, 0x9A, 0x5D, 0x6F, 0x96, 0xE1, 0x74, 0xB5,
+    0xD3, 0x44, 0x91, 0xA8, 0x45, 0x0C, 0xE2, 0x3D, 0xAC, 0x85, 0xF9, 0x3B, 0x5B, 0x19, 0x8A, 0x43, 0x1F, 0xCA, 0x50,
+    0x9D, 0x87, 0xD2, 0x0F, 0xC2, 0x1F, 0x89, 0x4F, 0x6D, 0x04, 0x0F, 0xE1, 0x61, 0xAA, 0xEE, 0xB4, 0x8E, 0x56, 0xFB,
+    0x06, 0xAF, 0x04, 0xF3, 0x40, 0x9B, 0x55, 0x4E, 0xCB, 0x66, 0x91, 0xCB, 0x18, 0xC2, 0x88, 0xB6, 0xB1, 0x65, 0x60,
+    0xA4, 0x6E, 0xDC, 0xA4, 0x9E, 0xAF, 0xE1, 0xBF, 0xC2, 0x2F, 0x89, 0xA9, 0xE1, 0xFB, 0x8D, 0x6E, 0xC2, 0x3B, 0x4B,
+    0x30, 0xD7, 0x60, 0xDA, 0x41, 0x2D, 0xCC, 0x6C, 0x2E, 0x49, 0xF3, 0x1E, 0x42, 0x19, 0x5D, 0x58, 0x3C, 0x8A, 0x81,
+    0x82, 0xB8, 0x0C, 0xC9, 0xF2, 0xE5, 0x8F, 0x03, 0x8F, 0x36, 0xE3, 0x8A, 0x98, 0xCC, 0x14, 0xAB, 0x62, 0x2B, 0xC2,
+    0x34, 0xA2, 0xA5, 0x78, 0x37, 0x42, 0x12, 0x70, 0x8C, 0x62, 0xD2, 0x6D, 0x72, 0x7B, 0xAF, 0x9B, 0xDD, 0xFD, 0xE5,
+    0x4E, 0x79, 0x49, 0x45, 0x73, 0xA9, 0x72, 0x2F, 0xF0, 0x73, 0x83, 0xF8, 0xCE, 0xB4, 0x33, 0xE8, 0x3F, 0xAE, 0x42,
+    0xF7, 0x76, 0xB3, 0x83, 0x57, 0xE5, 0x95, 0xBE, 0xCE, 0x8F, 0x7B, 0xDE, 0xD7, 0x4B, 0x6B, 0x9C, 0x1E, 0x8D, 0xF0,
+    0x56, 0x7B, 0xDD, 0x26, 0x34, 0x5F, 0x1F, 0xDB, 0x9D, 0x37, 0x53, 0xB8, 0x96, 0xED, 0xA0, 0x16, 0xB1, 0xC9, 0x2C,
+    0x8B, 0xF2, 0x26, 0x58, 0x89, 0x37, 0xEE, 0x04, 0xB2, 0x97, 0x54, 0x2D, 0x88, 0xC0, 0x60, 0x0B, 0x03, 0x5E, 0x9B,
+    0x67, 0xFB, 0x36, 0xE9, 0x31, 0x2D, 0x9C, 0x37, 0x9E, 0x32, 0x84, 0x5D, 0x2C, 0x4A, 0xD6, 0xAD, 0x73, 0x63, 0x28,
+    0x36, 0xAA, 0x53, 0xF7, 0x90, 0x29, 0x8E, 0x5C, 0x92, 0xBE, 0x41, 0xDC, 0xC0, 0xB3, 0x2B, 0x46, 0x32, 0x4B, 0x96,
+    0x35, 0xAD, 0x1F, 0xC2, 0xDF, 0x89, 0x17, 0xF6, 0xB6, 0xFA, 0xB5, 0xED, 0xB8, 0xB7, 0x8E, 0x78, 0x66, 0x96, 0x09,
+    0x6C, 0x6E, 0x23, 0x32, 0x28, 0x08, 0xE8, 0xF2, 0xBA, 0xF9, 0x86, 0x48, 0xC0, 0x68, 0xFE, 0x63, 0xC8, 0x23, 0x82,
+    0xCC, 0xA5, 0x4A, 0xFA, 0x66, 0x8F, 0xF0, 0x37, 0xE2, 0x6D, 0xE5, 0xC9, 0x3A, 0x87, 0x86, 0xB4, 0xFB, 0x28, 0xAE,
+    0x61, 0x0F, 0x0B, 0x59, 0xDF, 0xC0, 0xD1, 0xAC, 0xE0, 0x24, 0x41, 0x42, 0xC4, 0x49, 0x1B, 0x10, 0x21, 0x50, 0xC0,
+    0x09, 0x11, 0x8B, 0xEE, 0x6E, 0x71, 0xE2, 0xE2, 0x78, 0xBB, 0x33, 0xFA, 0xC5, 0x1A, 0xB4, 0xEA, 0xC6, 0x74, 0xD2,
+    0x8C, 0x24, 0xA5, 0x2A, 0x3C, 0xB5, 0x2E, 0xB9, 0x9B, 0x71, 0x97, 0x34, 0xE0, 0xAA, 0x54, 0x93, 0x71, 0x56, 0x49,
+    0xB9, 0xC6, 0x4E, 0x9A, 0x9B, 0xD3, 0xFA, 0x7F, 0x81, 0xB8, 0xD6, 0xAC, 0xDD, 0x6F, 0x65, 0x8D, 0x82, 0x77, 0x85,
+    0x95, 0xE1, 0x7D, 0x1C, 0xD2, 0x8B, 0x7A, 0x27, 0xA2, 0xF4, 0xED, 0xEE, 0x9E, 0x67, 0xE0, 0x8F, 0x81, 0x37, 0xBA,
+    0xEF, 0x87, 0x67, 0xBF, 0x8F, 0xC4, 0xD2, 0xDD, 0x4F, 0x05, 0xA8, 0x61, 0x7B, 0x1E, 0x9E, 0xE1, 0x8C, 0xEA, 0xF3,
+    0x18, 0x99, 0xA3, 0xDE, 0x76, 0x66, 0x36, 0x2A, 0x30, 0xFB, 0x9B, 0x0F, 0xC3, 0x1C, 0xA3, 0x76, 0x4B, 0xFB, 0x3B,
+    0xE8, 0xBA, 0x66, 0xBF, 0x0E, 0x93, 0xFD, 0xAB, 0x23, 0xD9, 0xA5, 0xCE, 0x62, 0xF3, 0x34, 0xEB, 0x7F, 0x29, 0x0A,
+    0xA7, 0x04, 0x48, 0xF2, 0x79, 0x82, 0x42, 0x1D, 0x46, 0x4B, 0xA9, 0x1B, 0xD1, 0xBE, 0x52, 0x54, 0xD7, 0xA8, 0xF8,
+    0x33, 0xE1, 0xAF, 0xC4, 0xA8, 0x24, 0xD6, 0x6D, 0xED, 0xBC, 0x0A, 0xD3, 0x5A, 0x5C, 0xC4, 0xDF, 0x64, 0x17, 0x97,
+    0x36, 0xF0, 0x65, 0x52, 0x39, 0xD4, 0x23, 0x22, 0x9D, 0xD8, 0x64, 0x83, 0x04, 0x85, 0x38, 0xEF, 0xB8, 0x49, 0x91,
+    0xBB, 0xFF, 0x00, 0x0A, 0xDF, 0xE3, 0x77, 0x84, 0xAC, 0xD3, 0x4A, 0xBC, 0xF0, 0x3A, 0x5A, 0x5B, 0x4F, 0x72, 0x5E,
+    0xD7, 0x53, 0x8E, 0xE2, 0x12, 0x6D, 0xC6, 0x40, 0x20, 0x47, 0xE6, 0x3E, 0x71, 0x26, 0x70, 0x24, 0xE4, 0xB4, 0x63,
+    0x2A, 0xC0, 0xE0, 0x7E, 0x71, 0x98, 0x71, 0x35, 0x5C, 0x4E, 0x69, 0x5A, 0xBD, 0x7C, 0x7A, 0x9C, 0xE3, 0xC9, 0xCF,
+    0x38, 0x46, 0x8D, 0xA4, 0xDC, 0x63, 0x38, 0x4A, 0xE9, 0xED, 0x5A, 0x4E, 0x4A, 0x6D, 0xF3, 0xCA, 0x2D, 0xB9, 0x4D,
+    0xD3, 0x77, 0x8C, 0x7F, 0xA8, 0xF8, 0x53, 0x8D, 0x31, 0x32, 0xC8, 0xA9, 0xDB, 0x15, 0x04, 0x9F, 0xB4, 0xD2, 0xF4,
+    0xD3, 0xF8, 0xA5, 0x77, 0xCD, 0xB3, 0x49, 0x6C, 0xB4, 0xEA, 0x97, 0x46, 0x78, 0x45, 0xC4, 0x16, 0x5A, 0xDD, 0xA5,
+    0xA6, 0x8D, 0xA7, 0xEA, 0x77, 0x4A, 0x54, 0x47, 0x3C, 0x31, 0x41, 0x20, 0x06, 0x68, 0x00, 0x9A, 0x4F, 0x2A, 0x40,
+    0x5D, 0x5F, 0x69, 0xF3, 0x15, 0xCB, 0x32, 0x96, 0xDC, 0xC0, 0x90, 0xA5, 0xF0, 0xBD, 0xAF, 0xC3, 0x96, 0x83, 0x51,
+    0xB8, 0xD6, 0xA7, 0x48, 0xD2, 0xE8, 0x2B, 0x2C, 0x2D, 0x6B, 0xF6, 0xA4, 0x55, 0x8E, 0x45, 0x5F, 0xBA, 0x54, 0x2A,
+    0x36, 0x77, 0x12, 0x72, 0xE5, 0x9C, 0x14, 0x3B, 0x63, 0x6C, 0x62, 0x8A, 0x2B, 0xDE, 0xCD, 0x70, 0x74, 0xA7, 0x92,
+    0xE2, 0x31, 0x35, 0x2D, 0x29, 0x54, 0xBB, 0x97, 0xBB, 0x18, 0xF3, 0x38, 0x52, 0xA5, 0x38, 0xDF, 0x92, 0x31, 0x7E,
+    0xEB, 0x9B, 0x6A, 0xCD, 0x6B, 0xEF, 0x7C, 0x6E, 0x52, 0x7F, 0xE1, 0xF7, 0x0E, 0x54, 0x96, 0x1B, 0x3D, 0x52, 0x86,
+    0xF0, 0x73, 0x4B, 0xEE, 0x92, 0xD6, 0xD6, 0xBF, 0xC2, 0x8D, 0x9F, 0x0B, 0xDE, 0xEB, 0xF3, 0x69, 0x6B, 0x06, 0x9B,
+    0xA9, 0x5B, 0xE9, 0xF6, 0x6F, 0x76, 0x1E, 0x45, 0x8E, 0xE1, 0x54, 0xC8, 0xCD, 0xF3, 0x28, 0x8B, 0x1C, 0x9E, 0x25,
+    0x55, 0xDA, 0xA5, 0x58, 0x80, 0xCA, 0x46, 0x42, 0xA8, 0xF4, 0x1B, 0xEB, 0xBB, 0xBB, 0x8B, 0x69, 0xAF, 0xA5, 0x8E,
+    0xD0, 0x49, 0x25, 0x9C, 0x37, 0x73, 0xE9, 0xD7, 0xF2, 0x14, 0x8E, 0x55, 0x91, 0x64, 0x90, 0x46, 0xA8, 0xF9, 0x50,
+    0x57, 0x73, 0x2E, 0xE0, 0x55, 0xF6, 0x87, 0x45, 0x20, 0x2E, 0xC7, 0x28, 0xAF, 0xCD, 0x78, 0xA6, 0xA5, 0x5C, 0x26,
+    0x33, 0x01, 0x35, 0x2E, 0x67, 0x52, 0x35, 0xA0, 0xEE, 0x93, 0x56, 0x70, 0x4F, 0x48, 0xDB, 0x95, 0x6B, 0x76, 0xF4,
+    0xB4, 0xA5, 0x27, 0x29, 0x29, 0x35, 0x16, 0xBF, 0xA8, 0x7C, 0x3E, 0x92, 0xF6, 0x98, 0xA8, 0x5B, 0x4B, 0xC5, 0xDB,
+    0x5E, 0x8E, 0x4F, 0x7D, 0xFA, 0xDB, 0x57, 0xB2, 0x56, 0xD6, 0xED, 0xF7, 0x3E, 0x10, 0xB2, 0x82, 0xF6, 0xC2, 0xF2,
+    0xF3, 0x4E, 0xD4, 0xAF, 0xEE, 0x5A, 0xCA, 0xCE, 0xD2, 0xF1, 0xA7, 0xB8, 0x9D, 0xD4, 0x42, 0x8C, 0xF2, 0x3C, 0x8E,
+    0x42, 0x02, 0x24, 0xFD, 0xDA, 0x96, 0x60, 0xAD, 0xB0, 0xC9, 0x0E, 0x00, 0xC8, 0xC8, 0xEA, 0xEE, 0x12, 0x7B, 0x09,
+    0x6C, 0x6E, 0xCE, 0xA2, 0x0B, 0xAA, 0x32, 0xD9, 0xB9, 0x49, 0x66, 0xDF, 0x74, 0xCC, 0x31, 0x1B, 0xE4, 0xE6, 0x63,
+    0xF2, 0x91, 0x95, 0x42, 0x15, 0x8B, 0x7D, 0xE0, 0xAC, 0xB4, 0x51, 0x5F, 0x33, 0x3A, 0xD8, 0x8C, 0x46, 0x7A, 0x9C,
+    0xA6, 0xD7, 0x2C, 0x13, 0x49, 0x25, 0x6E, 0x6A, 0x73, 0xE4, 0x84, 0x9E, 0x9A, 0xC9, 0x29, 0x24, 0x9E, 0xE9, 0x42,
+    0x11, 0x8D, 0xA2, 0x9C, 0x5F, 0xF5, 0x37, 0x0D, 0x36, 0xF8, 0x7E, 0x9A, 0xEC, 0xE5, 0xE5, 0x7E, 0x67, 0x77, 0x7B,
+    0x7A, 0xBF, 0x5E, 0xB7, 0x3F, 0xFF, 0xD9,
+};
+
+// 8x8 progressive JPEG, 521 bytes
+static const uint8_t JPEG_PROGRESSIVE[] = {
+    0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46, 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00,
+    0x00, 0xFF, 0xDB, 0x00, 0x43, 0x00, 0x10, 0x0B, 0x0C, 0x0E, 0x0C, 0x0A, 0x10, 0x0E, 0x0D, 0x0E, 0x12, 0x11, 0x10,
+    0x13, 0x18, 0x28, 0x1A, 0x18, 0x16, 0x16, 0x18, 0x31, 0x23, 0x25, 0x1D, 0x28, 0x3A, 0x33, 0x3D, 0x3C, 0x39, 0x33,
+    0x38, 0x37, 0x40, 0x48, 0x5C, 0x4E, 0x40, 0x44, 0x57, 0x45, 0x37, 0x38, 0x50, 0x6D, 0x51, 0x57, 0x5F, 0x62, 0x67,
+    0x68, 0x67, 0x3E, 0x4D, 0x71, 0x79, 0x70, 0x64, 0x78, 0x5C, 0x65, 0x67, 0x63, 0xFF, 0xDB, 0x00, 0x43, 0x01, 0x11,
+    0x12, 0x12, 0x18, 0x15, 0x18, 0x2F, 0x1A, 0x1A, 0x2F, 0x63, 0x42, 0x38, 0x42, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63,
+    0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63,
+    0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0x63,
+    0x63, 0x63, 0x63, 0x63, 0x63, 0x63, 0xFF, 0xC2, 0x00, 0x11, 0x08, 0x00, 0x08, 0x00, 0x08, 0x03, 0x01, 0x22, 0x00,
+    0x02, 0x11, 0x01, 0x03, 0x11, 0x01, 0xFF, 0xC4, 0x00, 0x15, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0xFF, 0xC4, 0x00, 0x15, 0x01, 0x01, 0x01, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x05, 0xFF, 0xDA, 0x00, 0x0C, 0x03,
+    0x01, 0x00, 0x02, 0x10, 0x03, 0x10, 0x00, 0x00, 0x01, 0x94, 0x05, 0x3F, 0xFF, 0xC4, 0x00, 0x14, 0x10, 0x01, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08,
+    0x01, 0x01, 0x00, 0x01, 0x05, 0x02, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01, 0x03, 0x01, 0x01, 0x3F,
+    0x01, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01, 0x02, 0x01, 0x01, 0x3F, 0x01, 0x7F, 0xFF, 0xC4, 0x00,
+    0x14, 0x10, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0xFF, 0xDA, 0x00, 0x08, 0x01, 0x01, 0x00, 0x06, 0x3F, 0x02, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x10, 0x01, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01,
+    0x01, 0x00, 0x01, 0x3F, 0x21, 0x7F, 0xFF, 0xDA, 0x00, 0x0C, 0x03, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x00, 0x00,
+    0x10, 0x0B, 0xFF, 0xC4, 0x00, 0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01, 0x03, 0x01, 0x01, 0x3F, 0x10, 0x7F, 0xFF, 0xC4, 0x00,
+    0x14, 0x11, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0xFF, 0xDA, 0x00, 0x08, 0x01, 0x02, 0x01, 0x01, 0x3F, 0x10, 0x7F, 0xFF, 0xC4, 0x00, 0x14, 0x10, 0x01, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xDA, 0x00, 0x08, 0x01,
+    0x01, 0x00, 0x01, 0x3F, 0x10, 0x7F, 0xFF, 0xD9,
+};
+
+class SourceImage : public RuntimeImage {
+ public:
+  explicit SourceImage(image::ImageType type = image::IMAGE_TYPE_RGB, int width = 0, int height = 0)
+      : RuntimeImage(JPEG, type, image::TRANSPARENCY_OPAQUE, nullptr, false, width, height) {}
+  size_t decoded_bytes() const { return this->decoded_bytes_; }
+  int scale() const { return static_cast<const JpegDecoder *>(this->decoder_.get())->get_scale(); }
+};
+
+/// The file in memory; fails reads once fail_at bytes have been read
+class MemorySource : public DecodeSource {
+ public:
+  MemorySource(const uint8_t *data, size_t size, size_t fail_at = SIZE_MAX)
+      : data_(data), size_(size), fail_at_(fail_at) {}
+  int32_t read(uint8_t *buf, uint32_t len) override {
+    if (this->pos_ >= this->fail_at_)
+      return -1;
+    const size_t n = std::min<size_t>(len, this->size_ - this->pos_);
+    memcpy(buf, this->data_ + this->pos_, n);
+    this->pos_ += n;
+    this->reads++;
+    return static_cast<int32_t>(n);
+  }
+  bool seek(uint32_t position) override {
+    if (position > this->size_)
+      return false;
+    this->pos_ = position;
+    return true;
+  }
+  int reads{0};
+
+ protected:
+  const uint8_t *data_;
+  size_t size_;
+  size_t pos_{0};
+  size_t fail_at_;
+};
+
+/// Hands out only the bytes delivered so far, like a download that is still arriving
+class TrickleSource : public DecodeSource {
+ public:
+  TrickleSource(const uint8_t *data, size_t size, size_t delivered) : data_(data), size_(size), delivered_(delivered) {}
+  int32_t read(uint8_t *buf, uint32_t len) override {
+    const size_t n = std::min<size_t>(len, this->delivered_ - this->pos_);
+    memcpy(buf, this->data_ + this->pos_, n);
+    this->pos_ += n;
+    return static_cast<int32_t>(n);
+  }
+  bool seek(uint32_t position) override {
+    if (position > this->delivered_)
+      return false;
+    this->pos_ = position;
+    return true;
+  }
+  void deliver(size_t len) { this->delivered_ = std::min(this->size_, this->delivered_ + len); }
+
+ protected:
+  const uint8_t *data_;
+  size_t size_;
+  size_t delivered_;
+  size_t pos_{0};
+};
+
+static bool decode_fed(RuntimeImage &img) {
+  std::vector<uint8_t> buffer(JPEG_ROWS, JPEG_ROWS + sizeof(JPEG_ROWS));
+  if (!img.begin_decode(buffer.size()))
+    return false;
+  if (img.feed_data(buffer.data(), buffer.size()) != static_cast<int>(buffer.size()))
+    return false;
+  return img.end_decode();
+}
+
+/// Decodes from a source a step at a time; returns the last result and counts the steps
+static int decode_stepped(RuntimeImage &img, DecodeSource &source, int &steps) {
+  steps = 0;
+  if (!img.begin_decode(sizeof(JPEG_ROWS)) || !img.decoder_supports_source())
+    return DECODE_ERROR_UNSUPPORTED_FORMAT;
+  int result = img.begin_source(&source);
+  if (result != 0)
+    return result;
+  do {
+    result = img.decode_step();
+    steps++;
+  } while (result == DECODE_STEP_MORE);
+  if (result == DECODE_STEP_DONE && !img.end_decode())
+    return DECODE_ERROR_INTERNAL_DECODER_ERROR;
+  return result;
+}
+
+static std::vector<uint8_t> pixels(const RuntimeImage &img) {
+  const uint8_t *start = img.get_data_start();
+  return std::vector<uint8_t>(start, start + img.get_width_stride() * img.get_height());
+}
+
+TEST(JpegSourceDecode, SteppedDecodeMatchesFedDecode) {
+  SourceImage fed;
+  ASSERT_TRUE(decode_fed(fed));
+
+  SourceImage stepped;
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  int steps;
+  ASSERT_EQ(decode_stepped(stepped, source, steps), DECODE_STEP_DONE);
+  EXPECT_EQ(steps, 3);
+  ASSERT_EQ(stepped.get_width(), 48);
+  ASSERT_EQ(stepped.get_height(), 40);
+  EXPECT_EQ(pixels(stepped), pixels(fed));
+}
+
+TEST(JpegSourceDecode, SteppedDirectRgb565MatchesFedDecode) {
+  // A fixed size that is not a whole multiple of the source exercises the scaling tables across steps
+  SourceImage fed(image::IMAGE_TYPE_RGB565, 30, 25);
+  ASSERT_TRUE(decode_fed(fed));
+
+  SourceImage stepped(image::IMAGE_TYPE_RGB565, 30, 25);
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  int steps;
+  ASSERT_EQ(decode_stepped(stepped, source, steps), DECODE_STEP_DONE);
+  EXPECT_EQ(pixels(stepped), pixels(fed));
+}
+
+// decodeBegin() is given the same reduced scale as decode(), and decodeRows() keeps it for every step
+TEST(JpegSourceDecode, SteppedScaledDecodeMatchesFedDecode) {
+  for (auto type : {image::IMAGE_TYPE_RGB565, image::IMAGE_TYPE_RGB}) {
+    // 24x20 is half of 48x40, so JPEGDEC decodes at 1/2 size
+    SourceImage fed(type, 24, 20);
+    ASSERT_TRUE(decode_fed(fed));
+    ASSERT_EQ(fed.scale(), 2);
+
+    SourceImage stepped(type, 24, 20);
+    MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+    int steps;
+    ASSERT_EQ(decode_stepped(stepped, source, steps), DECODE_STEP_DONE);
+    ASSERT_EQ(stepped.scale(), 2);
+    EXPECT_EQ(pixels(stepped), pixels(fed)) << "image type " << type;
+  }
+}
+
+TEST(JpegSourceDecode, WaitsForDataThatHasNotArrived) {
+  SourceImage fed;
+  ASSERT_TRUE(decode_fed(fed));
+
+  // Enough for the headers (the scan starts at byte 609), then 50 bytes between steps
+  SourceImage img;
+  TrickleSource source(JPEG_ROWS, sizeof(JPEG_ROWS), 700);
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_ROWS)));
+  ASSERT_EQ(img.begin_source(&source), 0);
+  int waits = 0;
+  int result;
+  while ((result = img.decode_step()) == DECODE_STEP_MORE || result == DECODE_STEP_NEED_DATA) {
+    if (result == DECODE_STEP_NEED_DATA)
+      waits++;
+    source.deliver(50);
+    ASSERT_LT(waits, 1000);
+  }
+  ASSERT_EQ(result, DECODE_STEP_DONE);
+  ASSERT_TRUE(img.end_decode());
+  EXPECT_GT(waits, 0);
+  EXPECT_EQ(pixels(img), pixels(fed));
+}
+
+TEST(JpegSourceDecode, ImageIsHiddenUntilTheLastStep) {
+  SourceImage img;
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_ROWS)));
+  ASSERT_EQ(img.begin_source(&source), 0);
+  EXPECT_EQ(img.decode_step(), DECODE_STEP_MORE);
+  EXPECT_EQ(img.get_width(), 0);
+  EXPECT_EQ(img.get_data_start(), nullptr);
+}
+
+TEST(JpegSourceDecode, ReadFailureIsReportedAndTheDecoderRecovers) {
+  SourceImage img;
+  // The first read fills JPEGDEC's buffer, so the failure comes part way through the image data
+  MemorySource failing(JPEG_ROWS, sizeof(JPEG_ROWS), 2048);
+  int steps;
+  EXPECT_EQ(decode_stepped(img, failing, steps), DECODE_ERROR_READ);
+  EXPECT_GE(steps, 1);
+  img.release();
+
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  EXPECT_EQ(decode_stepped(img, source, steps), DECODE_STEP_DONE);
+}
+
+TEST(JpegSourceDecode, ReleasePartWayThroughLetsTheNextDecodeStart) {
+  SourceImage img;
+  MemorySource first(JPEG_ROWS, sizeof(JPEG_ROWS));
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_ROWS)));
+  ASSERT_EQ(img.begin_source(&first), 0);
+  ASSERT_EQ(img.decode_step(), DECODE_STEP_MORE);
+  img.release();
+  EXPECT_FALSE(img.is_decoding());
+
+  MemorySource second(JPEG_ROWS, sizeof(JPEG_ROWS));
+  int steps;
+  EXPECT_EQ(decode_stepped(img, second, steps), DECODE_STEP_DONE);
+  EXPECT_EQ(steps, 3);
+}
+
+TEST(JpegSourceDecode, FailedFirstReadIsAReadError) {
+  SourceImage img;
+  MemorySource failing(JPEG_ROWS, sizeof(JPEG_ROWS), 0);
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_ROWS)));
+  EXPECT_EQ(img.begin_source(&failing), DECODE_ERROR_READ);
+}
+
+TEST(JpegSourceDecode, FailedSeekToTheStartIsAReadError) {
+  class NoSeekSource : public MemorySource {
+   public:
+    using MemorySource::MemorySource;
+    bool seek(uint32_t position) override { return false; }
+  };
+  SourceImage img;
+  NoSeekSource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_ROWS)));
+  EXPECT_EQ(img.begin_source(&source), DECODE_ERROR_READ);
+  EXPECT_EQ(img.decode_step(), DECODE_ERROR_INVALID_TYPE);
+}
+
+TEST(JpegSourceDecode, ProgressiveImageIsUnsupported) {
+  SourceImage img;
+  MemorySource source(JPEG_PROGRESSIVE, sizeof(JPEG_PROGRESSIVE));
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_PROGRESSIVE)));
+  EXPECT_EQ(img.begin_source(&source), DECODE_ERROR_UNSUPPORTED_FORMAT);
+  EXPECT_EQ(img.decode_step(), DECODE_ERROR_INVALID_TYPE);
+}
+
+TEST(JpegSourceDecode, CompletedDecodeCountsTheWholeImage) {
+  SourceImage img;
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_ROWS)));
+  ASSERT_EQ(img.begin_source(&source), 0);
+  int result;
+  while ((result = img.decode_step()) == DECODE_STEP_MORE) {
+    EXPECT_EQ(img.decoded_bytes(), 0u);
+  }
+  ASSERT_EQ(result, DECODE_STEP_DONE);
+  EXPECT_EQ(img.decoded_bytes(), sizeof(JPEG_ROWS));
+}
+
+TEST(JpegSourceDecode, SourceIsReadAsTheDecodeNeedsIt) {
+  SourceImage img;
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  int steps;
+  ASSERT_EQ(decode_stepped(img, source, steps), DECODE_STEP_DONE);
+  EXPECT_GE(source.reads, 2);
+}
+
+TEST(JpegSourceDecode, DecodersThatCannotReadASourceSaySo) {
+  RuntimeImage img(BMP, image::IMAGE_TYPE_RGB, image::TRANSPARENCY_OPAQUE);
+  ASSERT_TRUE(img.begin_decode(100));
+  EXPECT_FALSE(img.decoder_supports_source());
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  EXPECT_EQ(img.begin_source(&source), DECODE_ERROR_UNSUPPORTED_FORMAT);
+  EXPECT_EQ(img.decode_step(), DECODE_ERROR_UNSUPPORTED_FORMAT);
+}
+
+TEST(JpegSourceDecode, SourceNeedsTheImageSize) {
+  SourceImage img;
+  MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));
+  // JPEGDEC needs the file size up front, and holds it in an int
+  ASSERT_TRUE(img.begin_decode(0));
+  EXPECT_EQ(img.begin_source(&source), DECODE_ERROR_INVALID_TYPE);
+  img.release();
+  ASSERT_TRUE(img.begin_decode(static_cast<size_t>(INT32_MAX) + 1));
+  EXPECT_EQ(img.begin_source(&source), DECODE_ERROR_INVALID_TYPE);
+}
+
+TEST(JpegSourceDecode, StepWithoutADecodeIsRefused) {
+  SourceImage img;
+  EXPECT_EQ(img.decode_step(), DECODE_ERROR_INVALID_TYPE);
+  ASSERT_TRUE(img.begin_decode(sizeof(JPEG_ROWS)));
+  // begin_source() was never called
+  EXPECT_EQ(img.decode_step(), DECODE_ERROR_INVALID_TYPE);
+}
+
+}  // namespace esphome::runtime_image::testing
+
+#endif  // USE_RUNTIME_IMAGE_JPEG

tests/unit_tests/components/test_wifi.py

@@ -4,7 +4,7 @@ from ipaddress import IPv4Address
 
 import pytest
 
-from esphome.components.esp32 import const
+from esphome.components.esp32 import KEY_ESP32, KEY_IDF_VERSION, const
 from esphome.components.network import (
     KEY_HIGH_PERFORMANCE_NETWORKING,
     KEY_HIGH_PERFORMANCE_WIFI,
@@ -241,6 +241,14 @@ def wisp_core(monkeypatch: pytest.MonkeyPatch, request: pytest.FixtureRequest) -
             KEY_FRAMEWORK_VERSION: params.get("idf", cv.Version(5, 4, 0)),
         },
     )
+    # The ESP-IDF underneath, which an Arduino build maps from its own version; only an
+    # ESP32 build has it
+    if params.get("platform", Platform.ESP32) == Platform.ESP32:
+        monkeypatch.setitem(
+            CORE.data,
+            KEY_ESP32,
+            {KEY_IDF_VERSION: params.get("idf", cv.Version(5, 4, 0))},
+        )
 
 
 def _wisp_ap(**overrides: object) -> dict:
@@ -300,18 +308,35 @@ def test_dns_servers_limited_to_two() -> None:
 
 @pytest.mark.parametrize(
     ("wisp_core", "valid"),
-    [({"idf": cv.Version(5, 5, 5)}, False), ({"idf": cv.Version(6, 0, 1)}, True)],
+    [
+        ({"idf": cv.Version(5, 5, 5)}, False),
+        ({"idf": cv.Version(6, 0, 1)}, True),
+        ({"framework": "arduino", "idf": cv.Version(5, 5, 6)}, False),
+        ({"framework": "arduino", "idf": cv.Version(6, 0, 1)}, True),
+    ],
     indirect=["wisp_core"],
 )
 def test_second_dns_server_requires_idf_6(wisp_core: None, valid: bool) -> None:
+    """The ESP-IDF underneath counts, so an Arduino build on ESP-IDF 6.0 gets it too."""
     ap = _wisp_ap(dns_servers=["1.1.1.1", "8.8.8.8"])
     if valid:
         wifi_network_ap(ap)
     else:
-        with pytest.raises(cv.Invalid, match="6.0.0"):
+        with pytest.raises(cv.Invalid, match="ESP-IDF 6.0"):
             wifi_network_ap(ap)
 
 
+@pytest.mark.parametrize(
+    "wisp_core",
+    [{"platform": Platform.ESP8266, "framework": "arduino"}],
+    indirect=True,
+)
+def test_second_dns_server_elsewhere_is_a_config_error(wisp_core: None) -> None:
+    """No ESP32 state to read a version from; the WISP platform check rejects it instead."""
+    with pytest.raises(cv.Invalid, match="only available on"):
+        wifi_network_ap(_wisp_ap(dns_servers=["1.1.1.1", "8.8.8.8"]))
+
+
 @pytest.mark.parametrize(
     "wisp_core",
     [{"platform": Platform.ESP8266, "framework": "arduino"}],