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LibGfx: Move webp bitmap decoding code into its own function

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Nico Weber 2023-04-04 09:33:19 -04:00 • committed by Linus Groh
parent e5e9d3b877
commit f21af311c2
1 changed files with 16 additions and 7 deletions
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23
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -443,6 +443,9 @@ static ErrorOr<PrefixCodeGroup> decode_webp_chunk_VP8L_prefix_code_group(WebPLoa
return group;
}
static ErrorOr<NonnullRefPtr<Bitmap>> decode_webp_chunk_VP8L_image(WebPLoadingContext&, VP8LHeader const& vp8l_header, LittleEndianInputBitStream&);
// 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)
@ -504,6 +507,12 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
}
}
context.bitmap = TRY(decode_webp_chunk_VP8L_image(context, vp8l_header, bit_stream));
return {};
}
static ErrorOr<NonnullRefPtr<Bitmap>> decode_webp_chunk_VP8L_image(WebPLoadingContext& context, VP8LHeader const& vp8l_header, LittleEndianInputBitStream& bit_stream)
{
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#623_decoding_entropy-coded_image_data
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#523_color_cache_coding
// spatially-coded-image = color-cache-info meta-prefix data
@ -546,7 +555,7 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
PrefixCodeGroup group = TRY(decode_webp_chunk_VP8L_prefix_code_group(context, color_cache_size, bit_stream));
context.bitmap = TRY(Bitmap::create(vp8l_header.is_alpha_used ? BitmapFormat::BGRA8888 : BitmapFormat::BGRx8888, context.size.value()));
auto bitmap = TRY(Bitmap::create(vp8l_header.is_alpha_used ? BitmapFormat::BGRA8888 : BitmapFormat::BGRx8888, context.size.value()));
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#522_lz77_backward_reference
struct Offset {
@ -575,8 +584,8 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
// lz77-coded-image =
// *((argb-pixel / lz77-copy / color-cache-code) lz77-coded-image)
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#623_decoding_entropy-coded_image_data
ARGB32* pixel = context.bitmap->begin();
ARGB32* end = context.bitmap->end();
ARGB32* pixel = bitmap->begin();
ARGB32* end = bitmap->end();
auto emit_pixel = [&pixel, &color_cache, color_cache_size, color_cache_code_bits](ARGB32 color) {
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#523_color_cache_coding
@ -639,17 +648,17 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
// "The smallest distance codes [1..120] are special, and are reserved for a close neighborhood of the current pixel."
if (distance <= 120) {
auto offset = distance_map[distance - 1];
distance = offset.x + offset.y * context.size->width();
distance = offset.x + offset.y * bitmap->physical_width();
if (distance < 1)
distance = 1;
} else {
distance = distance - 120;
}
if (pixel - context.bitmap->begin() < distance)
if (pixel - bitmap->begin() < distance)
return context.error("WebPImageDecoderPlugin: Backward reference distance out of bounds");
if (context.bitmap->end() - pixel < length)
if (bitmap->end() - pixel < length)
return context.error("WebPImageDecoderPlugin: Backward reference length out of bounds");
ARGB32* src = pixel - distance;
@ -668,7 +677,7 @@ static ErrorOr<void> decode_webp_chunk_VP8L(WebPLoadingContext& context, Chunk c
}
}
return {};
return bitmap;
}
static ErrorOr<VP8XHeader> decode_webp_chunk_VP8X(WebPLoadingContext& context, Chunk const& vp8x_chunk)