lhk229 b0a634dfd4 Add recolor pass to clean residual contamination colour
Add bgfilter/recolor.py: after despill, propagate clean neighbour chroma into
pixels whose colour is still off (residual green, or the magenta a green unmix
overshoots into), keeping luminance partway so hair texture survives. It installs
a real observed colour rather than subtracting, so it cannot overshoot. Despill
already neutralises the matte edge (off ~ 0 there), so recolor only touches the
contaminated interior and the wisps the dropout-fill rescued.

Runs as a final colour pass on the despilled foreground; pymatting + despill keep
their stronger edge handling. On the samples the magenta fringe drops sharply
(TestImage vis-magenta 0.065->0.014, TestImage2 0.085->0.031) with edge green
unchanged (vis-green ~0.02). Debug output color_mask.png replaces the despill /
foreground-background / foreground-correction maps; smoke updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-30 22:19:15 +08:00

BgFilter

Offline green screen character matting for AI-generated character images.

The first implementation follows the workflow in docs/green_screen_matting_workflow.md:

RGB input -> chroma confidence -> trimap -> ViTMatte -> alpha cleanup -> despill -> RGBA PNG -> QA previews

Environment

Use the conda environment lightML.

conda activate lightML
pip install -r requirements.txt

If the shell is not activated, call the environment Python directly:

D:\MiniConda\envs\lightML\python.exe -m bgfilter.cli --help

Single Image

D:\MiniConda\envs\lightML\python.exe -m bgfilter.cli `
  --input Samples\TestImage.png `
  --output Outputs\TestImage_rgba.png `
  --debug-dir Outputs\TestImage_debug `
  --config configs\default.yaml `
  --device cuda

The CLI reads configs/default.yaml when --config is provided. Command-line options override config values, so tuning can usually happen in YAML while runtime choices such as --device cpu stay on the command line.

Use CPU for validation when CUDA is unavailable:

D:\MiniConda\envs\lightML\python.exe -m bgfilter.cli `
  --input Samples\TestImage.png `
  --output Outputs\TestImage_rgba.png `
  --debug-dir Outputs\TestImage_debug `
  --config configs\default.yaml `
  --device cpu

Batch

D:\MiniConda\envs\lightML\python.exe -m bgfilter.cli `
  --input-dir Samples `
  --output-dir Outputs `
  --debug-dir Outputs\debug `
  --config configs\default.yaml `
  --device cuda

Chroma-Only Debug Mode

This mode skips ViTMatte and uses chroma confidence as an alpha seed. It is useful for fast debugging of chroma confidence, trimap, despill, and QA outputs.

D:\MiniConda\envs\lightML\python.exe -m bgfilter.cli `
  --input-dir Samples `
  --output-dir Outputs\chroma `
  --debug-dir Outputs\chroma_debug `
  --config configs\default.yaml `
  --matting-method chroma `
  --device cpu

Outputs

For each processed image, the CLI writes an RGBA PNG and optional debug files:

bg_confidence.png
trimap.png
alpha.png
foreground_rgb.png
foreground_background.png
foreground_correction.png
despill_mask.png
preview_black.png
preview_white.png
preview_gray.png
preview_red.png
preview_blue.png
qa_grid.png
metadata.json

Quality Check

The quality checker measures alpha validity and green spill on semi-transparent edge pixels.

D:\MiniConda\envs\lightML\python.exe -m bgfilter.quality_cli `
  Outputs\TestImage_rgba.png `
  --max-edge-green-excess-p95 0.30

Run the bundled sample smoke check:

D:\MiniConda\envs\lightML\python.exe scripts\smoke_samples.py `
  --samples-dir Samples `
  --output-dir Outputs\smoke_samples `
  --config configs\default.yaml `
  --device cpu `
  --fallback-to-chroma-alpha `
  --max-edge-green-excess-p95 0.30

Current Notes

  • Samples/ and Outputs/ are ignored by Git.
  • ViTMatte model weights are loaded from Hugging Face on first use.
  • Foreground color estimation uses pymatting's estimate_foreground_ml to propagate clean foreground colour into semi-transparent edges before final de-spill, writing the estimated foreground, background, and a correction map. Set foreground.method: unmix to fall back to the legacy heuristic.
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