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LibGfx/JPEGXL: Support images encoded with the YCbCr color space

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While being way less frequent than for classical JPEG images, JPEG XL
images can use the YCbCr color space. Supporting it makes us properly
decode the "The Smoke Machine" image on https://jpegxl.info/jxl-art.html
This commit is contained in:
Lucas CHOLLET 2023-08-10 23:51:11 -04:00 • committed by Jelle Raaijmakers
parent b34b80104f
commit f2c60b7716
Notes: sideshowbarker 2024-07-16 19:17:47 +09:00
1 changed files with 37 additions and 3 deletions
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40
Userland/Libraries/LibGfx/ImageFormats/JPEGXLLoader.cpp
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@ -2453,6 +2453,42 @@ static ErrorOr<void> apply_image_features(Image& image, ImageMetadata const& met
}
///
/// L.2 - XYB + L.3 - YCbCr
static void ycbcr_to_rgb(Image& image, u8 bits_per_sample)
{
auto& channels = image.channels();
VERIFY(channels.size() >= 3);
VERIFY(channels[0].width() == channels[1].width() && channels[1].width() == channels[2].width());
VERIFY(channels[0].height() == channels[1].height() && channels[1].height() == channels[2].height());
auto const half_range_offset = (1 << bits_per_sample) / 2;
for (u32 y = 0; y < channels[0].height(); ++y) {
for (u32 x = 0; x < channels[0].width(); ++x) {
auto const cb = channels[0].get(x, y);
auto const luma = channels[1].get(x, y);
auto const cr = channels[2].get(x, y);
channels[0].set(x, y, luma + half_range_offset + 1.402 * cr);
channels[1].set(x, y, luma + half_range_offset - 0.344136 * cb - 0.714136 * cr);
channels[2].set(x, y, luma + half_range_offset + 1.772 * cb);
}
}
}
static void apply_colour_transformation(Image& image, ImageMetadata const& metadata, Frame const& frame)
{
if (frame.frame_header.do_YCbCr)
ycbcr_to_rgb(image, metadata.bit_depth.bits_per_sample);
if (metadata.xyb_encoded) {
TODO();
} else {
// FIXME: Do a proper color transformation with metadata.colour_encoding
}
}
///
/// L.4 - Extra channel rendering
static ErrorOr<void> render_extra_channels(Image&, ImageMetadata const& metadata)
{
@ -2500,9 +2536,7 @@ public:
TRY(apply_image_features(image, m_metadata, frame));
// FIXME: Do a proper color transformation with metadata.colour_encoding
if (m_metadata.xyb_encoded || frame.frame_header.do_YCbCr)
TODO();
apply_colour_transformation(image, m_metadata, frame);
TRY(render_extra_channels(image, m_metadata));