UnemarsandClaude Opus 5.5 4649946900 Vibrance: Photoshop's Saturation and Vibrance, measured (linear light, 0.288 R + 0.712 G grey) (#1418) ...

Saturation −100 greyed to the HSL lightness, so a yellow (255, 255, 0) became grey 128 where
Photoshop shows near-white: a yellow logo with Brightness/Contrast +150 and Vibrance › Saturation
−100 clipped to it stayed yellow under Lighter Color. Measured black-box on Photoshop 25.4
(16-bit runs of 7,400-colour charts and HSV sweeps; sRGB, Adobe RGB and ProPhoto documents), both
sliders work in linear light through the document tone curve, Vibrance first, then Saturation:

- Saturation moves each colour from the grey 0.288 R + 0.712 G (blue has no weight, in every
  profile) by 1 + s, clipping per channel: within 0.07/255.
- Negative Vibrance is an HSV change in linear light keeping the hue, in closed form: 0.2/255 on
  average, the deepest shadows (V < 0.05) drift.
- Positive Vibrance: the brightness term is exact; the saturation boost (stronger for dull and
  dark colours, damped on reds and skin) is a fit, 0.4 (+10) to 5 (+100) /255 on average.

CPU (compose::adjust::vibrance_px) and GPU (compose.wgsl) share the constants; the parity test
gains a negative Vibrance and Saturation −100. photocraft-corpus adjustments/rgb8|rgb16/
vibrance.psd (Vibrance +60, Saturation −15): 25.6/255 mean, 89 max → 0.38 mean, 5 max.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

2026-10-08 18:28:42 -04:00

..

device_loss.rs

GPU: crash-safe startup and device-loss fallback (#243, #4) (#252) (#252)

2026-10-05 12:05:22 -04:00

parity.rs

Vibrance: Photoshop's Saturation and Vibrance, measured (linear light, 0.288 R + 0.712 G grey) (#1418)

2026-10-08 18:28:42 -04:00

vector_mask.rs

GPU: adapters without float render targets keep the GPU path for effect-free documents

2026-10-04 11:55:25 -04:00