Red Stamp Extractor
Red stamp extractor: upload a scanned stamp on white paper. HSV hue/saturation thresholding keeps the red ink and makes the background transparent — ready to overlay onto a contract PDF. In-browser, zero upload.
How to use
Purpose
Extract a red company seal or personal stamp from a scanned contract or invoice — convert the red marking into a transparent-background PNG to overlay onto digital contracts. Based on color thresholding (red hue + saturation > 50%) plus edge detection. Local processing.
Steps
- Upload a document scan containing a red stamp
- Tool auto-detects the red stamp region
- Fine-tune color threshold (default: red hue, saturation > 50%)
- Optional: edge sharpening
- Export transparent-background PNG
FAQ
- What stamp colors work?
- Standard red stamps (most common). Blue government / black personal stamps require manual color-threshold adjustment.
- Can I overlay it on a digital contract?
- Yes — open the contract in a PDF editor (Adobe / Foxit / Preview) and place the transparent PNG at the signature location. Note: image-only stamps have weak legal force — for legally-binding e-signatures, use a CA-certified service like e签宝 or DocuSign.
- What if the stamp is blurry?
- Scan at 300+ DPI for best extraction. Faded or unevenly-stamped originals extract poorly.
- Does it preserve the seal text?
- Yes — all red pixels are kept, including company name, anti-forgery marks, registration numbers.
- Is the contract uploaded?
- No — contracts and seals are commercially sensitive and processed strictly in-browser.
Use cases
- Overlay extracted stamp onto a digital contract
- Invoice archive with isolated stamp
- Company seal asset for branded documents
- Online agreement with branded stamp
- Document digitization workflow
Use cases
Extract red company seal to transparent PNG — local-only (contracts are sensitive). For legally-binding e-signatures, use a CA-certified service.