PDF Watermark Remover
Remove image-based watermarks from PDF files by surgically deleting the drawing instructions from
content streams and removing XObject resource references. This produces clean results with no
visible artifacts (no white/black rectangles, no color mismatches).
When to Use
- User wants to remove a watermark from a PDF
- User says "去水印", "remove watermark", "去掉水印", "去PDF水印"
- PDF has a "Made with Gamma", Canva, or similar branded watermark
- PDF has an image-based watermark in a corner or specific position
How It Works
The removal process targets the root cause — the PDF content stream instructions that draw the
watermark image — rather than covering or replacing the image:
- Detect: Scan each page for images matching watermark characteristics (position + size)
- Map: Build XObject name-to-xref mapping from the page's resource dictionary
- Remove from content stream: Delete the
q...cm.../Name Do...Qdrawing instruction - Remove from resources: Delete the watermark entry from the XObject dictionary
- Save with garbage collection to clean up orphaned objects
This approach leaves zero visual artifacts because the watermark simply never gets drawn.
Workflow
Step 1: Analyze the Watermark
Before running the script, determine the watermark's characteristics:
- Open the PDF and identify the watermark visually
- Note its position (typically bottom-right corner) and approximate size
- If it's a link (clickable), note the domain (e.g.
gamma.app)
Step 2: Run the Removal Script
Execute scripts/remove_watermark.py:
python scripts/remove_watermark.py <input.pdf> <output.pdf> [options]
Common options:
| Option | Default | Description |
|---|---|---|
--x-threshold |
700 | X position threshold — images with x0 > this value are candidates |
--min-w / --max-w |
100 / 200 | Width range for watermark detection |
--min-h / --max-h |
20 / 50 | Height range for watermark detection |
--remove-links |
off | Also remove link annotations |
--link-domain |
all | Only remove links containing this domain |
Gamma watermark example:
python scripts/remove_watermark.py input.pdf output.pdf --remove-links --link-domain gamma.app
Custom position watermark (e.g. top-left):
python scripts/remove_watermark.py input.pdf output.pdf --x-threshold 0 --min-w 50 --max-w 300 --min-h 10 --max-h 80
Step 3: Verify
Open the output PDF and check:
- Watermark is completely gone (no visual remnants)
- No color patches, rectangles, or artifacts in the watermark area
- Page content is otherwise intact
Troubleshooting
| Problem | Cause | Solution |
|---|---|---|
| Watermark still visible | Position/size doesn't match detection thresholds | Adjust --x-threshold, --min-w/max-w, --min-h/max-h |
| - Watermark still visible after adjustment | Watermark may be text-based, not image-based | This skill only handles image watermarks; for text watermarks, use redaction or content stream editing |
| Other images accidentally removed | Detection thresholds too broad | Narrow the width/height/position ranges |
| Black/white rectangle appears | Old approach used image replacement instead of content stream deletion | This skill uses content stream deletion — this should not happen |
Key Technical Insight
Why not overlay/replace? Three approaches that DON'T work well:
1. White rectangle overlay — Visible on non-white backgrounds, misses rounded corners
2. Image data replacement with 1x1 pixel — PDF renders the 1x1 pixel scaled up as a colored rectangle (black for transparent, white for white pixel)
3. delete_image API — Only clears image data, doesn't remove the XObject reference or content stream Do instruction; renders as blank/colored rectangle
The correct approach (used by this skill): Delete the Do instruction from the content stream
and the /Name xref R entry from the XObject dictionary. The watermark image data becomes an
orphaned object that gets garbage-collected on save.
Requirements
- Python 3.8+
- pymupdf (
pip install pymupdf)
