iop/basecurve: modernization, JzAzBz saturation, and gamut protection #20320
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This PR modernizes the basecurve module to better handle scene-referred workflows while maintaining strict backward compatibility. - Bump introspection to version 7. - UI Cleanup: removed hide graph and color balance. - New Feature: UCS Saturation Balance is now chroma-weighted (vibrance). - Legacy: Preserves exact behavior for existing edits.
This PR modernizes the basecurve module to improve its scene-referred capabilities while ensuring perfect backward compatibility for display-referred workflows. Key Improvements Scene-Referred Mode (ACES-like/Narkowicz): New Flow: Implements a perceptual tone mapping pipeline: Signal Analysis -> Matrix-based Looks -> Exposure Normalization -> Perceptual Tone Mapping -> RGB Reconstruction. Tone Mapping: Added ACES-like and Narkowicz perceptual models for better highlight roll-off and contrast control compared to standard curves. Looks: Added 3x3 RGB matrix-based 'Looks' (Portrait, Sky, etc.) with a mix slider. Color & Gamut Integrity: Perceptual Saturation (JzAzBz): Improved 'UCS saturation balance' to compress highlight saturation while boosting shadows for better visual density. Hue Correction: New color rotation slider with selective desaturation to eliminate common color drifts (skin tones, blues). Gamut Securing: Introduced a multi-space gamut engine (sRGB, Adobe RGB, Rec2020) and a specific Anti-Magenta Algorithm (Highlights Protection): Implementation of a selective highlight desaturation logic. When luminance exceeds the threshold (0.8), the compression factor is biased to be 10% stronger on the blue channel compared to red and green. Goal: This specifically targets the common 'magenta shift' in overexposed skies or artificial blue lights, ensuring they desaturate towards white rather than shifting hue. Ergonomics & Compatibility: Backward Compatibility: Display-referenced processing (classic mode) remains untouched. UI: Curve graph can now be resized with the mouse. Introspection: Bumped to version 7.
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This PR modernizes the basecurve module to improve its scene-referred capabilities while ensuring perfect backward compatibility for display-referred workflows.
Key Improvements
1. Scene-Referred Mode (ACES-like/Narkowicz):
◦ New Flow: Implements a perceptual tone mapping pipeline: Signal Analysis -> Matrix-based Looks -> Exposure Normalization -> Perceptual Tone Mapping -> RGB Reconstruction.
◦ Tone Mapping: Added ACES-like and Narkowicz perceptual models for better highlight roll-off and contrast control compared to standard curves.
◦ Looks: Added 3x3 RGB matrix-based "Looks" (Portrait, Sky, etc.) with a mix slider.
2. Color & Gamut Integrity:
◦ Perceptual Saturation (JzAzBz): Improved "UCS saturation balance" to compress highlight saturation while boosting shadows for better visual density.
◦ Hue Correction: New color rotation slider with selective desaturation to eliminate common color drifts (skin tones, blues).
◦ Gamut Securing: Introduced a multi-space gamut engine (sRGB, Adobe RGB, Rec2020) and a specific Anti-Magenta Algorithm (Highlights Protection): Implementation of a selective highlight desaturation logic. When luminance exceeds the threshold (0.8), the compression factor is biased to be 10% stronger on the blue channel compared to red and green.
◦ Goal: This specifically targets the common "magenta shift" in overexposed skies or artificial blue lights, ensuring they desaturate towards white rather than shifting hue.
3. Ergonomics & Compatibility:
◦ Backward Compatibility: Display-referenced processing (classic mode) remains untouched.
◦ UI: Curve graph can now be resized with the mouse.
◦ Introspection: Bumped to version 7.