AutoWBColorMatch

Overview

AutoWBColorMatch aligns an image’s white balance and global colour characteristics to match a reference. Multiple strategies are available: gray-world and highlight-based white balance, full or luminance-only Reinhard colour transfer in Lab space, or a hybrid pipeline that combines highlight balancing with Reinhard matching.

Inputs

image (IMAGE): Source image tensor [B, H, W, C]. Alpha channels are discarded.
reference (IMAGE): Target look that the source should emulate.
method (STRING, default "wb_highlight+reinhard"):
- wb_grayworld – scales channels so the global mean becomes neutral grey.
- wb_highlight – computes gains from the brightest pixels.
- reinhard_lab – matches full Lab mean/std to the reference.
- lab_l_only – matches only the L component in Lab space.
- wb_highlight+reinhard – performs highlight white balance first, then full Reinhard matching.
percentile (FLOAT, default 95.0): Percentile used by the highlight detector when wb_highlight is involved (range 80.0–99.9).
strength (FLOAT, default 1.0): Blends between the original (0.0) and fully matched result (1.0).
clip_gamut (BOOLEAN, default True): Clamps the final output to [0, 1] after blending.
force_size (BOOLEAN, default False): When True, resizes both images to the supplied target_width/target_height before computing statistics, then resizes the matched output back to the original resolution.
target_width, target_height (INT, defaults 1440×1080): Working resolution used when force_size is enabled.

Outputs

IMAGE: RGB tensor after white balance and colour matching, blended according to strength.

Processing Notes

Colour conversions follow the sRGB ↔ linear ↔ XYZ ↔ Lab pipeline with D65 white point constants.
Highlight-based white balance uses a quantile mask to estimate channel gains, clamping them between 0.5 and 2.0 to avoid extreme corrections.
Reinhard matching calculates per-image mean and standard deviation in Lab space; lab_l_only preserves chroma while adjusting luminance.
When force_size is active, corrections occur at the specified working resolution for improved speed and comparability; the result is then resampled back to match the original dimensions.

Tips

Use wb_highlight+reinhard to neutralise both colour casts and overall contrast in a single step.
Dial down strength to keep some of the original styling when the reference is only a loose guide.
Disable clip_gamut if you plan to perform additional tone mapping afterward and want to preserve unclamped intermediate values.*** End Patch

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