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* 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>