convert-to-webp

A command-line tool to batch-convert images to WebP format with optional image and/or text watermarks.
It automatically resizes, optimizes for quality, reports per-file and total byte/MB savings, and supports customization of fonts, colors, sizes and transparency.

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Features

• Convert JPEG/PNG to WebP with thumbnail resizing
• Optimize output with adjustable quality (0–100) and optimize/method=6 flags
• Image watermark: supply a PNG (with alpha) and set transparency
• Text watermark: customize text, TTF font, font size, font color, and transparency
• Reporting: shows bytes and MB saved per file and overall, plus percent reduction
• Batch processing: handle multiple files in one command

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Requirements

• Python 3.6+
• Pillow

pip install --upgrade Pillow

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Installation

1. Clone this repository

git clone https://github.com/behindsecurity/convert-to-webp.git
cd convert-to-webp

2. Make the script executable (or invoke via python3)

chmod +x convert-to-webp.py

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Usage

./convert-to-webp.py [options] <file1> <file2> ... <fileN>

All converted files are written to the ./webp/ directory (created automatically).

Common options

Option	Type	Default	Description
--quality	int	85	WebP quality (0=lowest…100=highest)
--prefix	string	''	Prefix for output filenames
--width	int	1024	Max width (px) for thumbnail
--height	int	1024	Max height (px) for thumbnail
--watermark	path	—	Path to image watermark (PNG with transparency recommended)
--transparency	int	100	Watermark image transparency (0=hidden…255=opaque)
--text	string	—	Text to render as watermark
--font-path	path	—	Path to .ttf font file (falls back to default PIL font)
--font-size	int	36	Font size for text watermark
--font-color	string	#FFFFFF	Font color, either hex (#rrggbb) or r,g,b
--text-transparency	int	100	Text watermark transparency (0=hidden…255=opaque)

Run ./convert-to-webp.py --help for full usage details.

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Examples

Basic conversion

./convert-to-webp.py photo1.jpg photo2.png

Set quality and resize dimensions

./convert-to-webp.py --quality 75 --width 800 --height 600 img/*.jpg

Add an image watermark

./convert-to-webp.py --watermark logo.png --transparency 128 pictures/*.png

Add a text watermark

./convert-to-webp.py \
  --text "© MyCompany" \
  --font-path /usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf \
  --font-size 48 \
  --font-color "#FF0000" \
  --text-transparency 200 \
  assets/*.jpg

Combined image + text watermark with output prefix

./convert-to-webp.py \
  --prefix "webp_" \
  --watermark logo.png --transparency 80 \
  --text "behindsecurity.com" \
  --font-size 30 \
  --font-color 255,255,0 \
  --text-transparency 150 \
  photos/*

After running, you’ll see output like:

Processed photo1.jpg -> ./webp/webp_photo1.webp
 → Saved 1,024,512 bytes (0.98 MB), 45.3% smaller
Processed photo2.png -> ./webp/webp_photo2.webp
 → Saved786,432 bytes (0.75 MB), 38.1% smaller

=== Overall Savings ===
Processed 2 images
Total saved: 1,810,944 bytes (1.73 MB), 41.7% smaller overall

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Contributing

1. Fork the repo
2. Create a feature branch (git checkout -b feature-name)
3. Commit your changes (git commit -m "Add feature")
4. Push to your branch (git push origin feature-name)
5. Open a Pull Request

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License

This project is licensed under the MIT License.