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* 32-bit: legacy Brightness/Contrast, Channel Mixer, Photo Filter and B&W tint unclipped In 32-bit documents Photoshop keeps these adjustments' results above 1 and below 0. On the photoshop corpus's rgb32/gray32 files: - Legacy Brightness/Contrast pivots its contrast at 127 of 255 (8/16-bit: 128) and is exact on every pixel. - Channel Mixer cuts each source percentage to 1/1024 toward zero, counts 255/512 of the constant and is exact on pure red, green, blue, black and white. - Photo Filter works on the linear samples, negative results included. - The Black & White tint is the Color blend mode without the clip at 1, as the blend mode is there; white tints to (1.05, 1.00, 0.87). We clipped all four to 0..1. The GPU kernels follow suit under F_HDR (the legacy pivot and the mixer's steps come from the planner), and the HDR parity test covers them. Photoshop oracles: rgb32 and gray32 brightness-contrast-legacy, rgb32 channel-mixer and black-white-tint pass (145 -> 149 of 258); floor 145 -> 149. rgb32 photo-filter improves (0.19 -> 0.035 max); the rest is its colour (#3790). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Masks: feathers blur with exactly the feather's variance A mask feather is a Gaussian with sigma = feather, which we approximate with three box passes per axis. Whole-pixel boxes rounded the variance: a 6 px feather blurred like 6.48 px and a 3 px one like 3.46 px, so feathered edges were too soft by up to 4 levels against Photoshop (psd-tools mask-parameters-no-real-channel.psd: a 6 px vector and 3 px pixel feather). Each pass is now an "extended box" (Gwosdek et al. 2011): weight 1 on the whole radius and a fractional weight on the two samples beyond it, so three passes have variance sigma^2 exactly. It stays O(n), reusing the window's leaving sample for the low end weight (50 MP at a 1000 px feather: 180 ms parallel, was 172). psd-tools: mask-parameters-no-real-channel 0.0168 -> 0.0060 (PASS), layer_mask_data.psd 26.9 % -> 3.9 % of pixels off (psb 25.9 % -> 1.8 %). Corpus test 239 -> 240; floor 236 -> 240. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Threshold: split on Photoshop's luminosity of whole samples Photoshop's Threshold splits on the luminosity 0.30 R + 0.59 G + 0.11 B (the blend modes' lum, as Gradient Map uses), not the Rec. 601 grey, taken over the document's whole sample values: - 8 bits: 30 R + 59 G + 11 B > 100 level - 50, i.e. the luminosity rounded to a level with halves down reaches the level; - 16 bits: 30 R + 59 G + 11 B >= 100 x the level in 16 bits (round(level x 32768 / 255): mid grey 16448 is level 128); - 32 bits: the luminosity reaches the level. Exact on every pixel of psd-tools threshold_rgb (36432 px; Rec. 601 split 28 the other way), threshold_16bits_rgb (100) and threshold_16bits_ grayscale, and the photoshop corpus's rgb16 threshold-128. The sums are exact in f32, on the CPU and in the GPU kernel, so ties (grey exactly on the level) split the same way on both. psd-tools: threshold_rgb and threshold_16bits_rgb pass; corpus test 239 -> 241, floor 236 -> 241. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Posterize: 16-bit documents bin the 16-bit sample, as Photoshop does At 16 bits Photoshop doesn't round to 8-bit levels before binning. It bins the 16-bit sample, floor(v16 * n / 32768), and lands on 8-bit levels through a 16-bit step: floor(b * 32768 / (n - 1)), converted with floor((o * 255 + 16384) / 32768). So the middle of 3 levels is 128 where 8 bits give 127, while 42.5 and 25.5 stay 42 and 25. Exact on every sample of psd-tools posterize_16bits_rgb (levels 3, 7, 13, 21) and posterize_16bits_grayscale (2, 6, 9, 11); the 8-bit rule missed up to half the range at bin edges. The same rule applies to CMYK and Lab channels at 16 bits: on the stored inks (#4945's native path) psd-tools posterize_16bits_cmyk goes from 4.26 % to 0.01 % of pixels off. 8-bit Posterize is unchanged. The GPU kernel runs the same rule; 16-bit layers reach it as half floats, so a sample within their precision of a bin edge can land in the neighbouring bin there (the CPU, which exports, is exact). psd-tools 239 -> 241; floor 236 -> 241. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * Groups: a pass-through clipping base with an adjustment renders isolated A pass-through group composites its children straight into the backdrop, so an adjustment layer inside reaches the layers beneath. When the group is the base of a clipping group and holds an adjustment layer, Photoshop renders it isolated instead: in psd-tools passthrough_clipping_mask_adjustment an Exposure in such a group leaves the layers beneath alone (we darkened them: half the image 170 levels off). The same group with a Linear Dodge child and no adjustment keeps reaching the backdrop (passthrough_clipping_mask_blendmode), and so do clipping-mask3/4/5, so the rule is the adjustment, not the clipping alone (isolating every pass-through clipping base broke those two). CPU compositor and GPU plan alike. psd-tools 239 -> 240; floor 240. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Brandon Thomas <echelon@gmail.com>