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LibGfx: Implement SUBTRACT_GREEN_TRANSFORM for webp lossless decoder

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This commit is contained in:
Nico Weber 2023-04-03 19:53:38 -04:00 • committed by Linus Groh
parent cdc77f7512
commit 8760376abe
1 changed files with 19 additions and 1 deletions
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20
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -636,6 +636,23 @@ public:
Transform::~Transform() = default;
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#43_subtract_green_transform
class SubtractGreenTransform : public Transform {
public:
virtual ErrorOr<void> transform(Bitmap&) override;
};
ErrorOr<void> SubtractGreenTransform::transform(Bitmap& bitmap)
{
for (ARGB32& pixel : bitmap) {
Color color = Color::from_argb(pixel);
u8 red = (color.red() + color.green()) & 0xff;
u8 blue = (color.blue() + color.green()) & 0xff;
pixel = Color(red, color.green(), blue, color.alpha()).value();
}
return {};
}
}
// https://developers.google.com/speed/webp/docs/riff_container#simple_file_format_lossless
@ -702,7 +719,8 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
case COLOR_TRANSFORM:
return context.error("WebPImageDecoderPlugin: VP8L COLOR_TRANSFORM handling not yet implemented");
case SUBTRACT_GREEN_TRANSFORM:
return context.error("WebPImageDecoderPlugin: VP8L SUBTRACT_GREEN_TRANSFORM handling not yet implemented");
TRY(transforms.try_append(TRY(try_make<SubtractGreenTransform>())));
break;
case COLOR_INDEXING_TRANSFORM:
return context.error("WebPImageDecoderPlugin: VP8L COLOR_INDEXING_TRANSFORM handling not yet implemented");
}