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LibGfx/WebP: Tell decode_webp_chunk_VP8() if it needs an alpha channel

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decode_webp_chunk_VP8() itself will only ever decode RGB data from a
lossy webp stream, but a separate ALPH chunk could add alpha data
later on. Let the function know if that will happen, so that it can
return a bitmap with an alpha channel if appropriate.

Since lossy decoding isn't implemented yet, no behavior change. But it
makes it a bit easier to implement lossy decoding in the future.
This commit is contained in:
Nico Weber 2023-05-07 21:25:31 -04:00 • committed by Andreas Kling
parent e13c319972
commit d15dc28833
1 changed files with 5 additions and 5 deletions
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10
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -283,18 +283,18 @@ static ErrorOr<VP8Header> decode_webp_chunk_VP8_header(Chunk const& vp8_chunk)
return VP8Header { version, show_frame, size_of_first_partition, width, horizontal_scale, height, vertical_scale };
}
static ErrorOr<NonnullRefPtr<Bitmap>> decode_webp_chunk_VP8(Chunk const& vp8_chunk)
static ErrorOr<NonnullRefPtr<Bitmap>> decode_webp_chunk_VP8(Chunk const& vp8_chunk, bool include_alpha_channel)
{
VERIFY(vp8_chunk.type == FourCC("VP8 "));
auto bitmap_format = include_alpha_channel ? BitmapFormat::BGRA8888 : BitmapFormat::BGRx8888;
// Uncomment this to test ALPH decoding for WebP-lossy-with-alpha images while lossy decoding isn't implemented yet.
#if 0
auto vp8_header = TRY(decode_webp_chunk_VP8_header(vp8_chunk));
// FIXME: probably want to pass in the bitmap format based on if there's an ALPH chunk.
return Bitmap::create(BitmapFormat::BGRA8888, { vp8_header.width, vp8_header.height });
return Bitmap::create(bitmap_format, { vp8_header.width, vp8_header.height });
#else
// FIXME: Implement webp lossy decoding.
(void)bitmap_format;
return Error::from_string_literal("WebPImageDecoderPlugin: decoding lossy webps not yet implemented");
#endif
}
@ -641,7 +641,7 @@ static ErrorOr<NonnullRefPtr<Bitmap>> decode_webp_image_data(ImageData const& im
}
VERIFY(image_data.image_data_chunk.type == FourCC("VP8 "));
auto bitmap = TRY(decode_webp_chunk_VP8(image_data.image_data_chunk));
auto bitmap = TRY(decode_webp_chunk_VP8(image_data.image_data_chunk, image_data.alpha_chunk.has_value()));
if (image_data.alpha_chunk.has_value())
TRY(decode_webp_chunk_ALPH(image_data.alpha_chunk.value(), *bitmap));