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LibGfx/JPEG: Support RGB JPEGs

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By default, JPEGs use YCbCr to encode colors however other encoding
exist. This patch adds the logic to determine which transformation is
needed and support for RGB encoded JPEGs :^).
This commit is contained in:
Lucas CHOLLET 2023-03-04 21:37:11 -05:00 • committed by Andreas Kling
parent c60338e187
commit a47d775be6
1 changed files with 70 additions and 1 deletions
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71
Userland/Libraries/LibGfx/JPEGLoader.cpp
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@ -1246,6 +1246,75 @@ static void ycbcr_to_rgb(JPEGLoadingContext const& context, Vector<Macroblock>&
}
}
static void signed_rgb_to_unsigned(JPEGLoadingContext const& context, Vector<Macroblock>& macroblocks)
{
for (u32 vcursor = 0; vcursor < context.mblock_meta.vcount; vcursor += context.vsample_factor) {
for (u32 hcursor = 0; hcursor < context.mblock_meta.hcount; hcursor += context.hsample_factor) {
for (u8 vfactor_i = 0; vfactor_i < context.vsample_factor; ++vfactor_i) {
for (u8 hfactor_i = 0; hfactor_i < context.hsample_factor; ++hfactor_i) {
u32 mb_index = (vcursor + vfactor_i) * context.mblock_meta.hpadded_count + (hcursor + hfactor_i);
for (u8 i = 0; i < 8; ++i) {
for (u8 j = 0; j < 8; ++j) {
macroblocks[mb_index].r[i * 8 + j] = clamp(macroblocks[mb_index].r[i * 8 + j] + 128, 0, 255);
macroblocks[mb_index].g[i * 8 + j] = clamp(macroblocks[mb_index].g[i * 8 + j] + 128, 0, 255);
macroblocks[mb_index].b[i * 8 + j] = clamp(macroblocks[mb_index].b[i * 8 + j] + 128, 0, 255);
}
}
}
}
}
}
}
static ErrorOr<void> handle_color_transform(JPEGLoadingContext const& context, Vector<Macroblock>& macroblocks)
{
if (context.color_transform.has_value()) {
// https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-T.872-201206-I!!PDF-E&type=items
// 6.5.3 - APP14 marker segment for colour encoding
switch (*context.color_transform) {
case ColorTransform::CmykOrRgb:
if (context.components.size() == 4) {
// FIXME: implement CMYK
dbgln("CMYK isn't supported yet");
} else if (context.components.size() == 3) {
signed_rgb_to_unsigned(context, macroblocks);
} else {
return Error::from_string_literal("Wrong number of components for CMYK or RGB, aborting.");
}
break;
case ColorTransform::YCbCr:
ycbcr_to_rgb(context, macroblocks);
break;
case ColorTransform::YCCK:
// FIXME: implement YCCK
dbgln("YCCK isn't supported yet");
break;
}
return {};
}
// No App14 segment is present, assuming :
// - 1 components means grayscale
// - 3 components means YCbCr
// - 4 components means CMYK
if (context.components.size() == 4) {
// FIXME: implement CMYK
dbgln("CMYK isn't supported yet");
}
if (context.components.size() == 3)
ycbcr_to_rgb(context, macroblocks);
if (context.components.size() == 1) {
// FIXME: This is what we used to do for grayscale,
// we should at least document it and maybe change it.
ycbcr_to_rgb(context, macroblocks);
}
return {};
}
static ErrorOr<void> compose_bitmap(JPEGLoadingContext& context, Vector<Macroblock> const& macroblocks)
{
context.bitmap = TRY(Bitmap::create(BitmapFormat::BGRx8888, { context.frame.width, context.frame.height }));
@ -1457,7 +1526,7 @@ static ErrorOr<void> decode_jpeg(JPEGLoadingContext& context)
auto macroblocks = TRY(construct_macroblocks(context));
dequantize(context, macroblocks);
inverse_dct(context, macroblocks);
ycbcr_to_rgb(context, macroblocks);
TRY(handle_color_transform(context, macroblocks));
TRY(compose_bitmap(context, macroblocks));
context.stream.clear();
return {};