Signature Extractor

读取用户提供的签名照片或扫描件，按 solid、hd、extract 三种模式用亮度、红色通道和饱和度三重过滤分离黑色墨迹、排除红色印章，可选 3 倍放大与锐化，输出 RGBA 透明背景 PNG，并报告输出尺寸与墨迹像素数。

anhao6170

热度 16.59

最近更新 2026-05-26 11:47:06

分类：效率依赖：代码执行 / 读写文件应用场景：文件转换

安装技能

复制下面的话术发给你的 Agent，它会通过 secure-skills 检索并安装该技能。

执行命令安装此 skill： npx secure-skills-cli add signature-extractor

Metadata

name: signature-extractor
version: 1.0.0
description: Extract clean, transparent-background signature ink from photos. Use when: user provides a photo of a handwritten signature and asks to remove the background, make signature transparent, upscale resolution, deepen/darken ink, or remove red stamps/seals. NOT for: general photo background removal (use remove.bg or similar), color signature ink extraction, or document scanning/OCR tasks.
user-invocable: true
metadata: {"openclaw":{"requires":{"bins":["python3"],"anyBins":[]},"emoji":"🖊️"}}

Signature Extractor

Extract handwritten signature ink from photographs or scanned documents, producing a clean transparent-background PNG. Removes white/light backgrounds, red stamps/seals, and colored paper textures while preserving black ink strokes.

When to Run

User provides an image and asks to "remove background from signature", "make signature transparent", "extract signature", "remove stamp/印章"
User asks to "darken signature ink", "make ink bolder", "填满笔迹", "加深签名"
User asks to "upscale signature", "make signature clearer", "提高签名清晰度"
User says "去掉底色", "去除背景", "签名透明", "提取签名", "去除印章"

Workflow

Identify the user's desired mode from their request:

Request keywords	Mode	What it does
"填满", "加深", "实心", "加粗", "solid", default	`solid`	3x upscale + sharpen + pure black opaque ink
"高清", "放大", "清晰", "upscale", "hd"	`hd`	3x upscale + sharpen + smooth alpha gradient
"去掉底色", "提取", "简单去掉", "quick", "extract"	`extract`	Original size extraction with alpha gradient

Run the extraction script:
```
python3 {baseDir}/scripts/extract_signature.py INPUT_IMAGE OUTPUT.png --mode MODE [--scale N]
```
- Default scale is 3 (for solid and hd modes). Adjust --scale if user specifies a different multiple.
- Output is always RGBA PNG format.
After completion, report: output dimensions, ink pixel count, and share the result with the user.

How It Works

The script isolates black ink using a three-channel color filter:

Brightness filter — pixels darker than a threshold are ink candidates
Red channel filter — R minus G must be less than 40, which excludes red stamps/seals
Saturation filter — low saturation ensures only true black/grey ink is captured, not colored marks

For solid and hd modes: LANCZOS upscaling → UnsharpMask sharpening → ink extraction → Alpha channel smoothing.

Prerequisites

pip install Pillow numpy