AutoAdjustNode

Overview

AutoAdjustNode performs a chained series of global tone corrections on an RGB image. It can optionally apply automatic levels, per-channel or monochrome tone stretching, neutral colour balancing in YCbCr, and a final horizontal flip. The implementation assumes floating-point tensors in [0, 1] and always returns RGB output.

Inputs

image (IMAGE): Source image tensor shaped [B, H, W, C] (C must be 3 or 4; the alpha channel is discarded).
precision (STRING): Selects percentile estimation mode for level/tone calculations. "Histogram (fast)" approximates quantiles via 256-bin histograms, while "Exact" uses torch.quantile.
auto_levels (BOOLEAN, default True): Enables global min/max remapping based on luma percentiles.
levels_shadow_clip_pct (FLOAT, default 0.1): Percentage of darkest pixels to clip when computing the low anchor for levels.
levels_highlight_clip_pct (FLOAT, default 0.1): Percentage of brightest pixels to clip when computing the high anchor.
levels_gamma_normalize (BOOLEAN, default False): When enabled, nudges midtones toward 50% grey if the median luma falls between 35% and 65%.
auto_tone (BOOLEAN, default True): Toggles the tone mapping stage.
tone_mode (STRING, default "Per-channel"): "Per-channel" stretches each channel independently; "Monochromatic" applies a single stretch derived from luma.
tone_shadow_clip_pct (FLOAT, default 0.1): Shadow percentile used by the tone stage.
tone_highlight_clip_pct (FLOAT, default 0.1): Highlight percentile used by the tone stage.
auto_color (BOOLEAN, default True): Enables neutral balance in YCbCr space (centres Cb/Cr components).
snap_neutral_midtones (BOOLEAN, default False): When True, only midtone pixels (luma in 0.2–0.8) contribute to the Cb/Cr statistics, reducing highlight/shadow bias.
flip_horizontal (BOOLEAN, default False): Horizontally mirrors the result.

Outputs

IMAGE: The processed RGB tensor with all three stages (levels, tone, colour) applied in order, plus any optional flip.

Processing Notes

All stages operate on float32 tensors in [0, 1]; the node casts incoming data accordingly and clamps the final output.
Levels and tone stages guard against degenerate ranges (when high equals low) and fall back to minimal stretching.
The colour balance stage works in YCbCr and uses either masked medians or simple means depending on snap_neutral_midtones.
Alpha channels are intentionally dropped so downstream nodes always receive RGB tensors.

Tips

Theoretically, use "Histogram (fast)" when performance matters or when feeding large batches; switch to "Exact" for reproducibility-sensitive work. In actual practice, "Exact" is usually faster, so there's no reason not to use it.
Keep levels_shadow_clip_pct/levels_highlight_clip_pct at zero when you need strict dynamic range preservation (e.g., HDR preparation).
Combine this node with AutoColorConfigNode to share toggle states across multiple branches of a workflow.*** End Patch

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