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* fix(render): an RGB colour in an isolated DeviceCMYK group blends in CMYK, as its ink Part of #4887. An isolated DeviceCMYK group blended in CMYK only when every colour in it had process tints (DeviceCMYK, DeviceGray); one RGB fill sent the whole group back to RGB blending. Vendored hayro-interpret patch (104): Color::ink_tints gives DeviceRGB, CalRGB, Lab and three-component ICCBased colours the ink that draws back to them through the bundled CMYK profile (new cmyk_inverse module: black 0.4*k0^2 + 0.6*k0^8 with k0 = 1 - max(r, g, b), matched to Acrobat on synthetic pages; then cyan, magenta and yellow by at most 12 Newton steps against the profile; one-entry per-thread cache). ICCBased CMYK still has no tints. Test an_rgb_colour_in_an_isolated_cmyk_group_blends_as_its_ink: 50% grey under Difference with black within 10 levels of Acrobat's 137 112 106; in-gamut colours draw as themselves; red within 8 of Acrobat's 238 32 37. With the additive arms reverted the grey draws 93 97 96 and it fails. #5228's control now uses an RGB image, which still has no tints. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * fix(render): an RGB colour with a non-finite component has no CMYK ink `to_rgba` turns a non-finite component into some finite colour, so the inverse could not see it and gave that colour's ink. `ink_from_srgb` now declines such a colour and the group draws it as before. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> --------- Co-authored-by: KenM76 <KenM76> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>