appleboy/resize-tool

Go Image Resize Tool

Go Image Resize Tool

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A simple yet powerful image resizing tool built with Go.

Table of Contents

• Go Image Resize Tool
  • Table of Contents
  • Features
  • Installation
    • Install via Script
      • Script Customization
    • Build from Source
    • Direct Usage
  • Usage
    • Show Help
    • Basic Usage
    • CLI Advanced Usage
  • Parameters
  • Output Filename Format
  • Examples
    • 1. Batch Process Multiple Images
    • 2. Website Image Optimization
    • 3. Create Thumbnails
    • 4. Other Useful Examples
  • Supported Image Formats
  • Build Instructions
  • Performance Tips
  • Error Handling
  • Technical Details
    • Libraries Used
    • Image Processing Algorithms
  • License

Features

• Support for multiple image formats: JPEG, PNG, GIF, TIFF, BMP
• 🎯 Smart Aspect Ratio: When only width or height is specified, the other dimension is automatically calculated proportionally
• Flexible resizing options
• Aspect ratio preservation options
• Adjustable JPEG quality
• Batch processing for directories
• Parallel processing for improved efficiency
• Custom output directories
• Detailed progress and size information display

Installation

Install via Script

You can install the latest prebuilt binary for your platform using the provided install script:

curl -fsSL https://raw.githubusercontent.com/appleboy/resize-tool/main/install.sh | bash

Or with wget:

wget -qO- https://raw.githubusercontent.com/appleboy/resize-tool/main/install.sh | bash

By default, the binary will be installed to ~/.resize-tool/bin/resize-tool and added to your shell PATH automatically.

Script Customization

You can customize the installation by setting environment variables:

• VERSION: Install a specific version (default: latest release)
• INSTALL_DIR: Change the install directory (default: ~/.resize-tool/bin)
• CURL_INSECURE=true: Allow insecure SSL download (not recommended)

Example:

INSTALL_DIR="$HOME/bin" VERSION="1.2.3" bash <(curl -fsSL https://raw.githubusercontent.com/appleboy/resize-tool/main/install.sh)

After installation, restart your terminal or run source ~/.bashrc (or your shell config) to update your PATH.

Build from Source

git clone <your-repo>
cd resize-tool
go mod tidy
go build -o resize-tool .

Direct Usage

If you have the compiled binary, you can use it directly:

resize-tool [options] <image-file>

Usage

Show Help

resize-tool --help

Basic Usage

# Default resize to 800x600 pixels
resize-tool image.jpg

# 🎯 Specify only width, height auto-calculated proportionally (recommended)
resize-tool -w 1200 image.jpg

# 🎯 Specify only height, width auto-calculated proportionally (recommended)
resize-tool --height 800 image.jpg

# Specify exact dimensions (may distort)
resize-tool -w 1200 --height 800 image.jpg

# Specify dimensions but maintain aspect ratio (fit within bounds)
resize-tool -k -w 1200 --height 800 image.jpg

CLI Advanced Usage

# Set JPEG quality (1-100)
resize-tool -q 85 -w 1000 image.jpg

# Specify output directory
resize-tool -w 800 -o ./resized/ image.jpg

# Overwrite original files (no new filename with dimensions)
resize-tool -w 800 --overwrite image.jpg

# Batch process all images in directory
resize-tool -b -w 1200 /path/to/image/directory

# Batch process and overwrite original files
resize-tool -b -w 1200 --overwrite /path/to/image/directory

# Use multiple threads for batch processing
resize-tool -b --workers 8 -w 1920 /path/to/image/directory

# Verbose output mode
resize-tool -v -w 800 image.jpg

# Combine multiple options
resize-tool -w 1920 --height 1080 -q 90 -o ./output/ -k -v image.jpg

Parameters

Parameter	Short	Default	Description
--width	-w	0	Output width (pixels, 0=auto-calculate based on height)
--height		0	Output height (pixels, 0=auto-calculate based on width)
--quality	-q	95	JPEG quality (1-100)
--output	-o	same	Output directory (default: same as input)
--keep-ratio	-k	false	Keep aspect ratio when both width and height specified
--batch	-b	false	Batch process all images in directory
--workers		4	Number of parallel workers for batch processing
--verbose	-v	false	Enable verbose output
--overwrite		false	Overwrite original files instead of creating new ones
--help	-h		Show help message

Output Filename Format

Resized files will automatically include dimension information:

• Original file: photo.jpg
• Output file: photo_800x600.jpg

Note: When using --overwrite, the original file is replaced and no dimension suffix is added.

Examples

1. Batch Process Multiple Images

# Process all jpg files in current directory
for img in *.jpg; do
    ./resize-tool -w 1200 "$img"
done

# Process all png files in current directory (height only)
for img in *.png; do
    ./resize-tool --height 800 "$img"
done

2. Website Image Optimization

# Create three different sizes (smart aspect ratio)
./resize-tool -w 1920 -q 85 -o ./large/ image.jpg
./resize-tool -w 1200 -q 85 -o ./medium/ image.jpg
./resize-tool -w 600 -q 80 -o ./small/ image.jpg

3. Create Thumbnails

# Create square thumbnails (fixed size, may crop)
./resize-tool -w 300 --height 300 -o ./thumbnails/ image.jpg

# Create thumbnails (keep aspect ratio, max 300x300)
./resize-tool -w 300 --height 300 -k -o ./thumbnails/ image.jpg

4. Other Useful Examples

# Specify only width, height auto-calculated
./resize-tool -w 1200 image.jpg

# Specify only height, width auto-calculated
./resize-tool --height 800 image.jpg

# Specify both width and height (may distort)
./resize-tool -w 1200 --height 800 image.jpg

# Specify both width and height, keep aspect ratio (fit within bounds)
./resize-tool -k -w 1200 --height 800 image.jpg

# Set JPEG quality
./resize-tool -q 85 -w 1000 image.jpg

# Specify output directory
./resize-tool -w 800 -o ./resized/ image.jpg

# Overwrite original file (replace in place)
./resize-tool -w 800 --overwrite image.jpg

# Batch process all images in directory
./resize-tool -b -w 1200 /path/to/image/directory

# Batch process and overwrite original files
./resize-tool -b -w 1200 --overwrite /path/to/image/directory

# Batch process with multiple threads
./resize-tool -b --workers 8 -w 1920 /path/to/image/directory

# Verbose output mode
./resize-tool -v -w 800 image.jpg

# Combine multiple options (Note: --overwrite cannot be used with --output)
./resize-tool -w 1920 --height 1080 -q 90 -o ./output/ -k -v image.jpg

Supported Image Formats

• Input formats: JPEG, PNG, GIF, TIFF, BMP
• Output formats: Same as input format

Build Instructions

To build the tool from source:

go build -o resize-tool .

For cross-compiling (multi-platform builds):

make release  # Build for multiple platforms

Performance Tips

• Uses Lanczos algorithm for high-quality image resizing
• Large file processing may require more memory
• JPEG quality setting affects both file size and image quality

Error Handling

The tool automatically handles common error conditions:

• File not found
• Unsupported image formats
• Output directory creation failure
• Out of memory

Technical Details

Libraries Used

• github.com/disintegration/imaging - Image processing
• github.com/spf13/cobra - CLI interface

Image Processing Algorithms

• Resize algorithm: Lanczos (high quality)
• Aspect ratio preservation: Uses Fit method, scales image to fit within specified dimensions
• Force dimensions: Uses Resize method, may change aspect ratio

License

MIT License