Skip to content

Default to 444 and fix XYB Subsampling #136

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
jonnyawsom3 wants to merge 2 commits into
base: main
Choose a base branch
from
Open

Default to 444 and fix XYB Subsampling #136

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
8a614ec
Default 444
jonnyawsom3 Jun 3, 2025
d685563
Fix XYB subsampling
jonnyawsom3 Jun 3, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
34 changes: 26 additions & 8 deletions lib/extras/enc/jpegli.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -434,30 +434,48 @@ Status EncodeJpeg(const PackedPixelFile& ppf, const JpegSettings& jpeg_settings,
}
jpegli_set_cicp_transfer_function(&cinfo, cicp_tf);
jpegli_set_defaults(&cinfo);
// All factors need to be specified to subsample the blue channel
// for XYB. H and V are swapped between YCbCr and XYB.
if (!jpeg_settings.chroma_subsampling.empty()) {
if (jpeg_settings.chroma_subsampling == "444") {
cinfo.comp_info[0].h_samp_factor = 1;
cinfo.comp_info[0].v_samp_factor = 1;
} else if (jpeg_settings.chroma_subsampling == "440") {
cinfo.comp_info[0].h_samp_factor = 1;
cinfo.comp_info[0].v_samp_factor = 2;
if (jpeg_settings.xyb) {
cinfo.comp_info[0].h_samp_factor = 2;
cinfo.comp_info[0].v_samp_factor = 2;
cinfo.comp_info[1].h_samp_factor = 2;
cinfo.comp_info[1].v_samp_factor = 2;
cinfo.comp_info[2].h_samp_factor = 2;
cinfo.comp_info[2].v_samp_factor = 1;
}
} else if (jpeg_settings.chroma_subsampling == "422") {
cinfo.comp_info[0].h_samp_factor = 2;
cinfo.comp_info[0].v_samp_factor = 1;
if (jpeg_settings.xyb) {
cinfo.comp_info[0].h_samp_factor = 2;
cinfo.comp_info[0].v_samp_factor = 2;
cinfo.comp_info[1].h_samp_factor = 2;
cinfo.comp_info[1].v_samp_factor = 2;
cinfo.comp_info[2].h_samp_factor = 1;
cinfo.comp_info[2].v_samp_factor = 2;
}
} else if (jpeg_settings.chroma_subsampling == "420") {
cinfo.comp_info[0].h_samp_factor = 2;
cinfo.comp_info[0].v_samp_factor = 2;
if (jpeg_settings.xyb) {
cinfo.comp_info[0].h_samp_factor = 2;
cinfo.comp_info[0].v_samp_factor = 2;
cinfo.comp_info[1].h_samp_factor = 2;
cinfo.comp_info[1].v_samp_factor = 2;
cinfo.comp_info[2].h_samp_factor = 1;
cinfo.comp_info[2].v_samp_factor = 1;
}
} else {
return false;
}
for (int i = 1; i < cinfo.num_components; ++i) {
cinfo.comp_info[i].h_samp_factor = 1;
cinfo.comp_info[i].v_samp_factor = 1;
}
} else if (!jpeg_settings.xyb) {
// Default is no chroma subsampling.
cinfo.comp_info[0].h_samp_factor = 1;
cinfo.comp_info[0].v_samp_factor = 1;
}
jpegli_enable_adaptive_quantization(
&cinfo, TO_JXL_BOOL(jpeg_settings.use_adaptive_quantization));
Expand Down
10 changes: 1 addition & 9 deletions lib/jpegli/encode.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -795,6 +795,7 @@ void jpegli_set_colorspace(j_compress_ptr cinfo, J_COLOR_SPACE colorspace) {
jpeg_component_info* comp = &cinfo->comp_info[c];
comp->component_index = c;
comp->component_id = c + 1;
// Default is no chroma subsampling.
comp->h_samp_factor = 1;
comp->v_samp_factor = 1;
comp->quant_tbl_no = 0;
Expand All @@ -806,10 +807,6 @@ void jpegli_set_colorspace(j_compress_ptr cinfo, J_COLOR_SPACE colorspace) {
cinfo->comp_info[1].component_id = 'G';
cinfo->comp_info[2].component_id = 'B';
if (cinfo->master->xyb_mode) {
// Subsample blue channel.
cinfo->comp_info[0].h_samp_factor = cinfo->comp_info[0].v_samp_factor = 2;
cinfo->comp_info[1].h_samp_factor = cinfo->comp_info[1].v_samp_factor = 2;
cinfo->comp_info[2].h_samp_factor = cinfo->comp_info[2].v_samp_factor = 1;
// Use separate quantization tables for each component
cinfo->comp_info[1].quant_tbl_no = 1;
cinfo->comp_info[2].quant_tbl_no = 2;
Expand All @@ -825,11 +822,6 @@ void jpegli_set_colorspace(j_compress_ptr cinfo, J_COLOR_SPACE colorspace) {
cinfo->comp_info[2].quant_tbl_no = 1;
cinfo->comp_info[1].dc_tbl_no = cinfo->comp_info[1].ac_tbl_no = 1;
cinfo->comp_info[2].dc_tbl_no = cinfo->comp_info[2].ac_tbl_no = 1;
// Use chroma subsampling by default
cinfo->comp_info[0].h_samp_factor = cinfo->comp_info[0].v_samp_factor = 2;
if (colorspace == JCS_YCCK) {
cinfo->comp_info[3].h_samp_factor = cinfo->comp_info[3].v_samp_factor = 2;
}
}
}

Expand Down