watermark-remover

name	Watermark Remover
description	Remove visible Gemini AI watermarks from images using reverse alpha blending. Use when user mentions "remove watermark", "Gemini watermark", "去水印", or wants to clean AI-generated images.

Watermark Remover

Instructions

This skill removes visible Gemini AI watermarks from images using mathematically accurate reverse alpha blending. It is based on GeminiWatermarkTool by Allen Kuo.

Important Notes

• This tool removes VISIBLE watermarks only (the semi-transparent logo in bottom-right corner)
• It does NOT remove SynthID invisible watermarks - those are embedded during image generation and cannot be separated from the image
• Best results on: slides, documents, UI screenshots, diagrams, logos, text-heavy images
• Always backup original images before processing

How It Works

Gemini adds watermarks using alpha blending:

watermarked = alpha × logo + (1 - alpha) × original

This tool reverses the equation:

original = (watermarked - alpha × logo) / (1 - alpha)

Watermark Size Detection

The tool automatically detects watermark size based on image dimensions:

Image Size	Watermark	Position
W ≤ 1024 OR H ≤ 1024	48×48	Bottom-right, 32px margin
W > 1024 AND H > 1024	96×96	Bottom-right, 64px margin

Usage

Remove watermark from a single image (in-place):

uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove image.jpg

Remove watermark and save to new file:

uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove input.jpg output.jpg

Batch process a directory:

uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove ./input_folder/ ./output_folder/

Force specific watermark size:

# Force small (48x48) watermark
uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove image.jpg --force-small

# Force large (96x96) watermark
uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove image.jpg --force-large

Verbose output:

uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove image.jpg -v

Show tool information:

uv run .claude/skills/watermark-remover/scripts/watermark_remover.py info

Supported Formats

• Input: .jpg, .jpeg, .png, .webp, .bmp
• Output: Same as input format (preserves quality settings)

Examples

Example 1: Quick Watermark Removal

User request:

I have a Gemini-generated image with a watermark. Can you remove it?

You would:

1. Ask for the image path
2. Run the removal command:

   uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove /path/to/image.jpg -v
   

3. Confirm the watermark was removed

Example 2: Batch Processing

User request:

I have a folder of AI-generated images that all have watermarks. Can you clean them?

You would:

1. Process the entire directory:

   uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove ./gemini_images/ ./cleaned_images/ -v
   

2. Report how many images were processed

Example 3: Preserve Original

User request:

Remove the watermark but keep my original file intact.

You would:

1. Specify a different output path:

   uv run .claude/skills/watermark-remover/scripts/watermark_remover.py remove original.png cleaned.png -v
   

Troubleshooting

"The image doesn't look different after processing"

The watermark is semi-transparent. If the original background was similar to the watermark color (white), the difference may be subtle. Try viewing at 100% zoom in the watermark area (bottom-right corner).

"Wrong watermark size detected"

Use --force-small or --force-large to manually specify the watermark size.

"Alpha map not found"

The skill requires alpha mask files in the assets/ directory. If missing, run:

python3 .claude/skills/watermark-remover/scripts/extract_masks.py /path/to/GeminiWatermarkTool/assets/embedded_assets.hpp

Credits

• Original algorithm and masks by Allen Kuo
• Based on GeminiWatermarkTool (MIT License)
• Technical write-up: Removing Gemini AI Watermarks: A Deep Dive into Reverse Alpha Blending