The Generic CMYK oracle only runs where macOS ships that profile. The
same comparison (CMYK -> sRGB, 8-bit, relative colorimetric without
BPC, same bytes for both engines) with the built-in Coated FOGRA39
runs everywhere. Measured: max 10, p99 5, mean 0.89 codes; the worst
pixel matches an independent float computation, not moxcms.
With a LUT destination, sRGB white came out as 0.3-0.5 % C/M/Y through
Transform::eval and precise float conversions: the legacy Lab encoding
puts L* 100 at 0.996 and a* = 0 at 0.50001, between the BToA grid
nodes, and fix_white only patched the device-link node, so only the
table paths were right.
Transform: for every intent but absolute colorimetric (and proofs
without paper simulation), a pixel equal to the source's device white
gives exactly the destination's device white. fix_white still sets the
device-link node; the paths that do not read that node exactly (the
exact pipeline, float interpolation, and 8-bit lookups when white is no
node) compare each pixel with white once. No other colour changes.
device_white(Lab) had a* = b* = 0.5; Lab white is 128/255 in the v4
encoding, which is no node of the 33-point grid, so Lab sources take
the per-pixel check there too.
Profile: synth::CmykParams::white_on_node maps no ink to exactly
L* 100, a* = b* = 0 in the AToB and gives the BToA tables input curves
that put that white on a node holding no ink. The Coated FOGRA39
profile is regenerated with it and separates PCS white to 2e-5 ink
(was 0.5 %), so the step into white is as smooth as its neighbours.
The default parameters and the Photocraft profile are unchanged; its
white still falls between nodes, so its last grey step into white is
up to about 0.4 % C larger than the one before, as with lcms's
white-node fix, and the test allows that for this profile.
FOGRA39 accuracy against 16a66e1: AToB against the patches unchanged
(mean 0.07, p95 0.18, max 0.53 ΔE00), reference sRGB values unchanged
(max 0.76), Lab -> CMYK -> Lab p95 1.04 -> 1.07, max 2.54 -> 2.55
(mean 0.24).
The crate denies panics, but asserts and slice indexing were reachable
from arguments: pixel strides, buffers that are not whole pixels or a
destination shorter than the source, single-colour slices shorter than
the channel count, CLUT and pipeline dimensions, and LUT sizes.
Every such check now returns CmsError::InvalidArgument. Buffer
conversions validate once per call, before any pixel is written, so the
per-pixel loops carry no extra checks; internal callers that already
guarantee lengths use crate-private unchecked evaluation.
Pipeline, Clut and Lut3d keep their fields private (read through
accessors) so a validated value cannot be changed into one that panics.
Pipeline::new checks matrix shapes and channel counts; Clut::new and
Clut::sample check grid, outputs and the table size limit.
API changes (unreleased crate):
- Transform::eval, eval_fast, convert_u8/u16/f32, apply,
convert_bytes_many and from_pipeline return Result.
- Pipeline::new, extend and eval, Clut::new, sample, eval,
eval_trilinear and eval_multilinear return Result.
- GamutCheck::delta_e and out_of_gamut, Lut3d::from_transform,
LutFile::identity and from_fn, synth::cmyk_profile and coated_cmyk
return Result.
- Pipeline, Clut and Lut3d fields are read through methods.
aiongg
