CMYK went to RGB through display sRGB: CMYK -> sRGB (clamped) -> working RGB.
Into a wider space (Wide Gamut RGB, the 1998 primaries) that clipped every
colour sRGB can't hold - CMYK cyan's red channel landed at 99 instead of 0 -
and the black-point compensation setting had no effect (moxcms leaves it
unimplemented). An ICC CMYK profile now converts directly into the RGB
profile: into its primaries with linear curves, where compensation is a
linear remap from the profile's black (found by sending black through the
profile and reading it back), then onto its own curves. The canvas uses the
same conversion into sRGB, so what shows is what an RGB export writes.
Checked against Ghostscript with the same profiles (relative colorimetric,
compensation on and off): exports into Wide Gamut RGB and the sRGB display
agree within 1 level in 255. The built-in CMYK spaces are unchanged (Generic
CMYK compensates in its own model).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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