beenull/ladybird
1
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2024-09-29 16:21:29 +00:00
Code Issues Actions 5 Packages Projects Releases Wiki Activity

LibGfx/JPEG: Allow decoding more subsampling factors

Browse source 
We now allow all subsampling factors where the subsampling factors
of follow-on components evenly decode the ones of the first component.

In practice, this allows YCCK 2111, CMYK 2112, and CMYK 2111.
This commit is contained in:
Nico Weber 2024-01-14 18:48:43 -05:00 committed by Andrew Kaster
parent d99d086da3
commit 3616d14c80
Notes: sideshowbarker 2024-07-17 10:10:18 +09:00 
Author: https://github.com/nico
Commit: https://github.com/SerenityOS/serenity/commit/3616d14c80
Pull-request: https://github.com/SerenityOS/serenity/pull/22758
Reviewed-by: https://github.com/LucasChollet ✅
2 changed files with 4 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
Tests/LibGfx/TestImageDecoder.cpp
View file

@ -325,7 +325,7 @@ TEST_CASE(test_jpeg_ycck)
{
Array test_inputs = {
TEST_INPUT("jpg/ycck-1111.jpg"sv),
// TEST_INPUT("jpg/ycck-2111.jpg"sv), // FIXME: Enable once this decodes correctly
TEST_INPUT("jpg/ycck-2111.jpg"sv),
TEST_INPUT("jpg/ycck-2112.jpg"sv),
};

10
Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp
View file

@ -1287,12 +1287,9 @@ static ErrorOr<void> read_start_of_frame(JPEGStream& stream, JPEGLoadingContext&
return Error::from_string_literal("Unsupported luma subsampling factors");
}
} else {
// YCCK with just CC subsampled and K matching Y is fine.
auto const& y_component = context.components[0];
bool channel_matches_y_factor = component.sampling_factors == y_component.sampling_factors;
bool k_channel_matches_y = context.color_transform == ColorTransform::YCCK && i == 3 && channel_matches_y_factor;
if (((component.sampling_factors != SamplingFactors { 1, 1 }) && !k_channel_matches_y) || (i == 3 && !channel_matches_y_factor)) {
if (y_component.sampling_factors.horizontal % component.sampling_factors.horizontal != 0
|| y_component.sampling_factors.vertical % component.sampling_factors.vertical != 0) {
dbgln_if(JPEG_DEBUG, "Unsupported chroma subsampling factors: horizontal: {}, vertical: {}",
component.sampling_factors.horizontal,
component.sampling_factors.vertical);
@ -1589,8 +1586,7 @@ static void inverse_dct(JPEGLoadingContext const& context, Vector<Macroblock>& m
static void undo_subsampling(JPEGLoadingContext const& context, Vector<Macroblock>& macroblocks)
{
// The first component has sampling factors of context.sampling_factors, while the others
// are either 1x1 or for the 4th component also context.sampling_factors. See
// read_start_of_frame() which currently enforces these restrictions.
// divide the first component's sampling factors. This is enforced by read_start_of_frame().
// This function undoes the subsampling by duplicating the values of the smaller components.
// See https://www.w3.org/Graphics/JPEG/itu-t81.pdf, A.2 Order of source image data encoding.
//