[runtime_image] Report a failed seek to the start as a read error

Also limit the JPEGDEC pin comment to the fixes ESPHome uses: it never
crops, and refuses progressive images.

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

esphome/components/runtime_image/__init__.py

@@ -94,9 +94,8 @@ class JPEGFormat(Format):
         cg.add_define("USE_RUNTIME_IMAGE_JPEG")
         # 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, progressive images (skipped blocks, unused
-        # AC tables that fail to build), cropping, and two ARM NEON faults (swapped red and blue in the
-        # 4:2:0 RGB8888 path, writes past the row on clipped MCUs)
+        # 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)
         cg.add_library(
             "JPEGDEC",
             "1.8.4",

esphome/components/runtime_image/jpeg_decoder.cpp

@@ -229,10 +229,13 @@ int JpegDecoder::begin_source(DecodeSource *source) {
     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 (!source->seek(0) ||
-      !this->jpeg_.open(this, this->expected_size_, source_close_, source_read_, source_seek_, draw_callback)) {
+  if (!this->jpeg_.open(this, this->expected_size_, source_close_, source_read_, source_seek_, draw_callback)) {
     ESP_LOGE(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;

tests/components/runtime_image/test_jpeg_source.cpp

@@ -326,6 +326,19 @@ TEST(JpegSourceDecode, FailedFirstReadIsAReadError) {
   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, SourceIsReadAsTheDecodeNeedsIt) {
   SourceImage img;
   MemorySource source(JPEG_ROWS, sizeof(JPEG_ROWS));