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LibGfx: Add scaffolding for applying transforms to webp lossless decoder

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Each of the four transforms will inherit from this class.
This commit is contained in:
Nico Weber 2023-04-04 20:15:22 -04:00 • committed by Linus Groh
parent b15d3b2329
commit cdc77f7512
1 changed files with 19 additions and 0 deletions
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19
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -626,6 +626,18 @@ static ErrorOr<NonnullRefPtr<Bitmap>> decode_webp_chunk_VP8L_image(WebPLoadingCo
return bitmap;
}
namespace {
class Transform {
public:
virtual ~Transform();
virtual ErrorOr<void> transform(Bitmap&) = 0;
};
Transform::~Transform() = default;
}
// https://developers.google.com/speed/webp/docs/riff_container#simple_file_format_lossless
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#7_overall_structure_of_the_format
static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk const& vp8l_chunk)
@ -656,6 +668,7 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
// optional-transform = (%b1 transform optional-transform) / %b0
// "Each transform is allowed to be used only once."
u8 seen_transforms = 0;
Vector<NonnullOwnPtr<Transform>, 4> transforms;
while (TRY(bit_stream.read_bits(1))) {
// transform = predictor-tx / color-tx / subtract-green-tx
// transform =/ color-indexing-tx
@ -697,6 +710,12 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
auto format = vp8l_header.is_alpha_used ? BitmapFormat::BGRA8888 : BitmapFormat::BGRx8888;
context.bitmap = TRY(decode_webp_chunk_VP8L_image(context, ImageKind::SpatiallyCoded, format, context.size.value(), bit_stream));
// Transforms have to be applied in the reverse order they appear in in the file.
// (As far as I can tell, this isn't mentioned in the spec.)
for (auto const& transform : transforms.in_reverse())
TRY(transform->transform(*context.bitmap));
return {};
}