git:20260827.ae998b6 to git:20260827.d2b68b3

---

name: image-region-remove-key-color-app

description: >-

Interactive Gradio UI to paint a region and remove solid key-color background

(white / green / magenta) only inside that selection. Use when enclosed white

islands remain after border/both keying, for localized 白底抠图, paint-to-erase

chroma patches, or selective color-key cleanup before Godot sprite import.

---

# Image Region Remove Key Color App

Paint a **region mask** in a local Gradio UI, then remove **key-color pixels only inside that region** (global keying scoped to the brush). Preserves white/light subject pixels outside the paint strokes.

Use after [image-remove-white-background](../image-remove-white-background/SKILL.md) when edge flood fill leaves enclosed white islands (e.g. gaps inside a silhouette).

## Rules

- Run `app.py` through the **`image-region-remove-key-color-app` manifest entry** (`.dependency/image-region-remove-key-color-app/.venv/`). Never use host `python`, `py`, `python3`, or any interpreter outside `.dependency/`.

- `populated: false` is not a reason to skip. Install first, set `populated: true`, retry the same command.

- This skill is **interactive**: launch the UI, give the user the local URL, wait for them to paint / Apply / Download.

## Setup (first run)

From project root:

```bash

.dependency/python/python -m venv .dependency/image-region-remove-key-color-app/.venv

.dependency/image-region-remove-key-color-app/.venv/Scripts/python.exe -m pip install Pillow gradio

```

If `python -m venv` fails (missing `venv` / `ensurepip`), create the env with `virtualenv` from another populated skill venv, then install packages into the new env:

```bash

.dependency/rembg/.venv/Scripts/python.exe -m pip install virtualenv

.dependency/rembg/.venv/Scripts/python.exe -m virtualenv .dependency/image-region-remove-key-color-app/.venv

.dependency/image-region-remove-key-color-app/.venv/Scripts/python.exe -m pip install Pillow gradio

```

Register in `.dependency/manifest.json`:

```json

"image-region-remove-key-color-app": {

"populated": true,

"bin": ".dependency/image-region-remove-key-color-app/.venv/Scripts/python.exe"

}

```

Use `bin/python` on Unix.

## Quick Start

```bash

# Preload an image (opens http://127.0.0.1:7860)

.dependency/image-region-remove-key-color-app/.venv/Scripts/python.exe .ai/image-region-remove-key-color-app/app.py path/to/sprite.png

# Custom port, no auto-open browser (agent / headless)

.dependency/image-region-remove-key-color-app/.venv/Scripts/python.exe .ai/image-region-remove-key-color-app/app.py path/to/sprite.png --port 7861 --no-browser

```

Download uses the **same filename** as the source (forced `.png`). No share / no save-to-disk folder.

## UI workflow

2. Transparent areas appear as **gray** in the editor (download still has real alpha).

3. **Paint** over local white / chroma patches to remove.

4. Choose **Key color** / tolerance / feather if needed.

7. Click **Stop server** when done (or `Ctrl+C` in the terminal).

## Key color

Use the UI color picker (default `#FFFFFF`). CLI `--preset` only sets the initial color and tolerance:

| `--preset` | Key color | Default tolerance |

|------------|-----------|-------------------|

| `white` *(default)* | `#FFFFFF` | 25 |

| `green` | `#00FF00` | 40 |

| `magenta` | `#FF00FF` | 40 |

## Agent workflow

## Defaults

| Option | Default | Notes |

|--------|---------|-------|

| Download name | same as source (`.png`) | Prepared on Apply via `DownloadButton` |

| `--preset` | `white` | Match the batch key skill |

| `--tolerance` | preset-specific | Raise for gray fringes |

| `--feather` | `2` | Softens hole edges inside the paint mask |

| `--port` | `7860` | Change if busy |

| Share | off | `share=False`; no share UI |

## Troubleshooting

| Issue | Fix |

|-------|-----|

| Manifest / venv missing | Follow **Setup**; update manifest |

| `No paint strokes found` | Brush visibly over the white islands; ensure strokes are on the editor layers |

| Port in use | Pass `--port 7861` (etc.) |

| Gradio import error | Reinstall in the skill venv: `pip install -U Pillow gradio` |

## Related

- Full-image / batch keying: [image-remove-white-background](../image-remove-white-background/SKILL.md)

- AI matting: [image-remove-background](../image-remove-background/SKILL.md)