Banana Watermark Remover

A CLI tool to remove star-shaped AI watermarks from images using alpha unmixing.

How It Works

Some AI image generators add a semi-transparent star-shaped watermark to the bottom-right corner of generated images. This tool uses alpha unmixing to mathematically reverse the alpha compositing and recover the original pixels underneath.

The algorithm:

1. Detects watermark size based on image dimensions (48px or 96px)
2. Locates the watermark position (bottom-right corner)
3. Applies the inverse alpha blending formula: original = (watermarked - 255*alpha) / (1 - alpha)

Note: This only removes visible watermarks. It cannot remove invisible watermarks embedded in pixel data.

Installation

npm install -g banana-watermark-remover

Or use directly with npx:

npx banana-watermark-remover input.png output.png

Usage

# Basic usage - specify input and output
banana-watermark-remover input.png output.png

# Auto-naming - creates input_clean.png
banana-watermark-remover input.png

# Supports different formats
banana-watermark-remover input.png output.jpg
banana-watermark-remover input.webp output.webp

# Batch mode - process multiple files using glob patterns
banana-watermark-remover "images/*.png"
banana-watermark-remover "**/*.jpg"

Note: When using glob patterns, output paths are auto-generated (e.g., image.png becomes image_clean.png). You cannot specify a custom output path in batch mode.

Supported Formats

• PNG (recommended)
• JPEG
• WebP

Requirements

• Node.js 22+
• Images must have a compatible star-shaped watermark in the bottom-right corner

Watermark Detection

The tool automatically selects the correct watermark configuration:

| Image Size | Logo Size | Margin | |------------|-----------|--------| | <=1024px (either dimension) | 48x48px | 32px | | >1024px (both dimensions) | 96x96px | 64px |

Local Development

# Clone the repository
git clone https://github.com/jantimon/banana-watermark-remover.git
cd banana-watermark-remover

# Install dependencies
npm install

# Build
npm run build

# Run locally
node dist/index.js input.png output.png

License

MIT License - see LICENSE for details.

Disclaimer

This tool is provided for educational and personal use. Users are responsible for ensuring their use complies with applicable terms of service and local regulations.