PDF2IMG

A Go-based command-line tool to convert PDF files to images (PNG/JPEG) with customizable translucent watermarks.

Features

• PDF to Image Conversion: Convert PDF pages to high-quality PNG or JPEG images (300 DPI)
• Customizable Watermarks: Add translucent text watermarks with full customization
• System Font Support: Automatically detects and uses system fonts (Microsoft YaHei preferred on Windows)
• Cross-Platform: Works on Windows, macOS, and Linux
• Windows/MinGW Compatible: Uses WebAssembly-based PDF rendering (no CGO required)
• Tiled Watermarks: Diagonal watermark pattern covering entire page

Installation

From Source

git clone https://github.com/KawaiiSh1zuku/pdf2img.git
cd pdf2img

Turn to go-pdfium for further information.

Requirements

• Go 1.21 or later
• pdfium library

Usage

pdf2img -i <input.pdf> [options]

Flags

Flag	Description	Default
-i	Input PDF file path (required)	-
-o	Output directory path	output
-f	Output format: png or jpg	png
-w	Watermark text	CONFIDENTIAL
-color	Watermark RGB color (format: R,G,B)	255,0,0 (red)
-opacity	Watermark opacity (0-100)	30
-size	Watermark font size	48
-sx	Horizontal spacing between watermarks	200
-sy	Vertical spacing between watermarks	150
-r	Watermark rotation angle (degrees)	45
-font	Path to custom TTF/TTC font file	auto-detect
-dpi	Rendering DPI	300

Examples

Basic Usage

# Convert PDF to PNG with default settings
pdf2img -i document.pdf

# Convert to JPEG
pdf2img -i document.pdf -f jpg

# Specify output directory
pdf2img -i document.pdf -o ./my_images

Watermark Customization

# Custom watermark text
pdf2img -i document.pdf -w "DRAFT COPY"

# Blue watermarks with 50% opacity
pdf2img -i document.pdf -color "0,100,200" -opacity 50

# Dense horizontal watermarks
pdf2img -i document.pdf -r 0 -sx 150 -sy 100

# Large red watermarks
pdf2img -i document.pdf -size 72 -color "255,0,0" -opacity 40

Custom Font

# Use specific font file
pdf2img -i document.pdf -font "/path/to/font.ttf" -w "Custom Font"

# Windows with Microsoft YaHei
pdf2img -i document.pdf -font "C:\Windows\Fonts\msyh.ttc"

Font Detection

The program automatically searches for fonts in priority order:

Windows

1. C:\Windows\Fonts\msyh.ttc (Microsoft YaHei)
2. C:\Windows\Fonts\msyh.ttf
3. Other CJK fonts (SimHei, SimSun, etc.)
4. Western fonts (Arial, Segoe UI)
5. User font directory

macOS

• /Library/Fonts
• /System/Library/Fonts
• ~/Library/Fonts

Linux

• /usr/share/fonts
• /usr/local/share/fonts
• ~/.fonts
• ~/.local/share/fonts

Output

Converted images are saved with the naming pattern:

<input_name>_page_1.png
<input_name>_page_2.png
<input_name>_page_3.png
...

Technical Details

PDF Rendering

• Uses go-pdfium with WebAssembly backend
• Uses CGO to lower memory usage

Image Processing

• Standard Go image package
• Bilinear interpolation for rotated watermarks
• Supports PNG and JPEG output

Troubleshooting

Font Not Found

If you see "Warning: no suitable system font found":

1. Install Microsoft YaHei or another TrueType font
2. Use -font flag to specify font path manually

Chinese Characters Not Displaying

1. Ensure Microsoft YaHei is installed (Windows)
2. Use -font to specify a CJK-compatible font
3. Verify the font file exists and is readable

Build Issues

# Ensure Go modules are enabled
go mod tidy

# Build for Windows (cross-compile from any OS)
GOOS=windows GOARCH=amd64 go build -o pdf2img.exe .

License

Apache License 2.0

Credits

• PDF rendering: go-pdfium by Klippa
• Font parsing: golang.org/x/image/font