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Watermark Usage Guide

This guide explains how to add watermarks to your PDFs during the build process.

Quick Start

Text Watermark

# Single chapter with text watermark
bubble-convert 1 --watermark "DRAFT"

# Full book with text watermark
bubble-build --watermark "CONFIDENTIAL"

Image Watermark

# Single chapter with image watermark
bubble-convert 1 --watermark-image path/to/logo.png

# Full book with image watermark
bubble-build --watermark-image path/to/watermark.png

Options

Text Watermark Options

  • --watermark TEXT: Watermark text (e.g., "DRAFT", "CONFIDENTIAL")
  • --watermark-opacity FLOAT: Opacity (0.0-1.0, default: 0.3)
  • --watermark-angle FLOAT: Rotation angle in degrees (default: 45)

Image Watermark Options

  • --watermark-image PATH: Path to watermark image (PNG, JPG, etc.)
  • --watermark-opacity FLOAT: Opacity (0.0-1.0, default: 0.3)
  • --watermark-angle FLOAT: Rotation angle in degrees (default: 45)

Examples

Example 1: Draft Watermark

bubble-convert 1 --watermark "DRAFT" --watermark-opacity 0.2 --watermark-angle 45

Example 2: Confidential Watermark

bubble-build --watermark "CONFIDENTIAL" --watermark-opacity 0.15

Example 3: Logo Watermark

bubble-build --watermark-image cover/logo.png --watermark-opacity 0.3

Example 4: Custom Watermark

bubble-convert chapter11-matrix-calculus \
  --watermark "FOR REVIEW" \
  --watermark-opacity 0.25 \
  --watermark-angle 30

Requirements

The watermark feature requires: - pypdf (for PDF manipulation) - reportlab (for watermark generation)

Install with: 

pip install pypdf reportlab

How It Works

  1. PDF is generated normally (via LaTeX/Pandoc)
  2. If watermark options are provided, the bubble-add-watermark script is called
  3. Watermark is applied as a post-processing step
  4. Original PDF is replaced with watermarked version

Performance

  • Speed: Adds ~1-5 seconds per PDF (depending on size)
  • Quality: No loss in PDF quality, watermark is added as a layer
  • Compatibility: Works with any PDF generated by the build system

Notes

  • Watermarks are applied after PDF generation
  • The original PDF is replaced (backup if needed)
  • Works with both single chapters and full book builds
  • Image watermarks are automatically scaled to fit the page