print::cmyk_blending(profile) blends transparency in CMYK and writes no
output intent or /Trapped, as a non-PDF/X print PDF does. print::settings
builds on it and adds the GTS_PDFX output intent and /Trapped /False.
Print PDFs written through krilla separated wrongly: transparency groups blended in RGB
(K 50% over C100 separated as C84 M34 Y32 K37 instead of C50 K50), and there was no
overprint, knockout, DeviceN, soft-mask backdrop or print output intent.
Patches in vendor/krilla/patches/, recorded in README.craft.md and SOURCE.json:
- 02 blending color space: GroupColorSpace { Rgb (default, unchanged output), Cmyk }
- 03 overprint: Surface::push_overprint (/op /OP /OPM)
- 04 knockout groups: Surface::push_group(GroupOptions { isolated, knockout })
- 05 soft-mask backdrop and transfer function (/BC /TR)
- 06 DeviceN and NChannel colors for fills and strokes
- 07 DeviceN images and shadings
- 08 print output intent (GTS_PDFX), /Trapped, PDF/X version markers
craft_pdf::write::print::settings(PrintColor) turns them on for print export.
aiongg