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WebP: Let ALPH replace alpha channel instead of augmenting it

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Pixels will leave the lossy decoder with alpha set to 255.
The old code would be a no-op in that case.

No observable behavior change yet, since there still is no
decoder for lossy webp.
This commit is contained in:
Nico Weber 2023-05-22 10:38:57 -04:00 • committed by Andreas Kling
parent 35fdc7f8c8
commit ae5d1d5a25
1 changed files with 2 additions and 2 deletions
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4
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -241,7 +241,7 @@ static ErrorOr<void> decode_webp_chunk_ALPH(Chunk const& alph_chunk, Bitmap& bit
if (alpha_data.size() < pixel_count)
return Error::from_string_literal("WebPImageDecoderPlugin: uncompressed ALPH data too small");
for (size_t i = 0; i < pixel_count; ++i)
bitmap.begin()[i] |= alpha_data[i] << 24;
bitmap.begin()[i] = alpha_data[i] << 24 | (bitmap.begin()[i] & 0xffffff);
return {};
}
@ -256,7 +256,7 @@ static ErrorOr<void> decode_webp_chunk_ALPH(Chunk const& alph_chunk, Bitmap& bit
return Error::from_string_literal("WebPImageDecoderPlugin: decompressed ALPH dimensions don't match VP8 dimensions");
for (size_t i = 0; i < pixel_count; ++i)
bitmap.begin()[i] |= (lossless_bitmap->begin()[i] & 0xff00) << 16;
bitmap.begin()[i] = (lossless_bitmap->begin()[i] & 0xff00) << 16 | (bitmap.begin()[i] & 0xffffff);
return {};
}