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LibGfx: Prepare the decoder to handle multiples scans

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This means that we should read markers in a loop instead of quiting on
the first scan. This is useless for now as `SOF0` frames only have one
scan, but this is a step forward `SOF2` support.
This commit is contained in:
Lucas CHOLLET 2023-02-19 23:37:30 -05:00 committed by Andreas Kling
parent c0c48afe06
commit bae37676c2
Notes: sideshowbarker 2024-07-17 18:46:57 +09:00 
Author: https://github.com/LucasChollet
Commit: https://github.com/SerenityOS/serenity/commit/bae37676c2
Pull-request: https://github.com/SerenityOS/serenity/pull/17562
Reviewed-by: https://github.com/nico ✅
1 changed files with 25 additions and 5 deletions
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30
Userland/Libraries/LibGfx/JPEGLoader.cpp
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@ -1184,9 +1184,7 @@ static ErrorOr<void> parse_header(AK::SeekableStream& stream, JPEGLoadingContext
case JPEG_SOF0:
TRY(read_start_of_frame(stream, context));
context.state = JPEGLoadingContext::FrameDecoded;
break;
case JPEG_SOS:
return read_start_of_scan(stream, context);
return {};
default:
if (auto result = skip_segment(stream); result.is_error()) {
dbgln_if(JPEG_DEBUG, "{}: Error skipping marker: {:x}!", TRY(stream.tell()), marker);
@ -1248,11 +1246,33 @@ static ErrorOr<void> decode_header(JPEGLoadingContext& context)
return {};
}
static ErrorOr<Vector<Macroblock>> construct_macroblocks(JPEGLoadingContext& context)
{
// B.6 - Summary
// See: Figure B.16 – Flow of compressed data syntax
// This function handles the "Multi-scan" loop.
Marker marker = TRY(read_marker_at_cursor(*context.stream));
while (true) {
if (is_miscellaneous_or_table_marker(marker)) {
TRY(handle_miscellaneous_or_table(*context.stream, context, marker));
} else if (marker == JPEG_SOS) {
TRY(read_start_of_scan(*context.stream, context));
TRY(scan_huffman_stream(*context.stream, context));
return TRY(decode_huffman_stream(context));
} else {
dbgln_if(JPEG_DEBUG, "{}: Unexpected marker {:x}!", TRY(context.stream->tell()), marker);
return Error::from_string_literal("Unexpected marker");
}
marker = TRY(read_marker_at_cursor(*context.stream));
}
}
static ErrorOr<void> decode_jpeg(JPEGLoadingContext& context)
{
TRY(decode_header(context));
TRY(scan_huffman_stream(*context.stream, context));
auto macroblocks = TRY(decode_huffman_stream(context));
auto macroblocks = TRY(construct_macroblocks(context));
dequantize(context, macroblocks);
inverse_dct(context, macroblocks);
ycbcr_to_rgb(context, macroblocks);