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fix: Handle grayscale data properly when encoding AVIFs #278

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fix: Handle grayscale data properly when encoding AVIFs #278

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53 changes: 34 additions & 19 deletions avif.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -702,8 +702,13 @@ size_t avif_encoder_write(avif_encoder e,
return 0;
}

// Determine pixel format based on input channels
// Grayscale (1 channel) -> YUV400 (monochrome)
// BGR (3 channels) or BGRA (4 channels) -> YUV444
const avifPixelFormat pixelFormat = (cvMat->channels() == 1) ? AVIF_PIXEL_FORMAT_YUV400 : AVIF_PIXEL_FORMAT_YUV444;

// Create AVIF image
avifImage* avifImage = avifImageCreate(cvMat->cols, cvMat->rows, 8, AVIF_PIXEL_FORMAT_YUV444);
avifImage* avifImage = avifImageCreate(cvMat->cols, cvMat->rows, 8, pixelFormat);
if (!avifImage) {
fprintf(stderr, "AVIF Encoder: failed to create image\n");
return 0;
Expand All @@ -729,24 +734,34 @@ size_t avif_encoder_write(avif_encoder e,
}
}

// Convert from BGR/BGRA to YUV
avifRGBImage rgb;
avifRGBImageSetDefaults(&rgb, avifImage);

// Set the correct pixel format based on input channels
rgb.format = cvMat->channels() == 4 ? AVIF_RGB_FORMAT_BGRA : AVIF_RGB_FORMAT_BGR;
rgb.depth = 8;
rgb.pixels = cvMat->data;
rgb.rowBytes = cvMat->step;
rgb.width = cvMat->cols;
rgb.height = cvMat->rows;

avifResult result = avifImageRGBToYUV(avifImage, &rgb);
if (result != AVIF_RESULT_OK) {
fprintf(
stderr, "AVIF Encoder: RGB to YUV conversion failed: %s\n", avifResultToString(result));
avifImageDestroy(avifImage);
return 0;
avifResult result;

// Handle grayscale images directly as YUV400
if (cvMat->channels() == 1) {
// Point the Y (luminance) plane directly at the grayscale data
avifImage->yuvPlanes[AVIF_CHAN_Y] = cvMat->data;
avifImage->yuvRowBytes[AVIF_CHAN_Y] = cvMat->step;
avifImage->imageOwnsYUVPlanes = AVIF_FALSE;
} else {
// Convert from BGR/BGRA to YUV
avifRGBImage rgb;
avifRGBImageSetDefaults(&rgb, avifImage);

// Set the correct pixel format based on input channels
rgb.format = cvMat->channels() == 4 ? AVIF_RGB_FORMAT_BGRA : AVIF_RGB_FORMAT_BGR;
rgb.depth = 8;
rgb.pixels = cvMat->data;
rgb.rowBytes = cvMat->step;
rgb.width = cvMat->cols;
rgb.height = cvMat->rows;

result = avifImageRGBToYUV(avifImage, &rgb);
if (result != AVIF_RESULT_OK) {
fprintf(
stderr, "AVIF Encoder: RGB to YUV conversion failed: %s\n", avifResultToString(result));
avifImageDestroy(avifImage);
return 0;
}
}

// Set up frame timing and flags
Expand Down