Image Resizer

A powerful command-line tool for resizing images by file size and/or dimensions, written in Rust.

Features

• Target File Size: Automatically compress images to stay under a specific file size (in KB)
• Dimension Resizing: Resize images to specific dimensions with optional aspect ratio maintenance
• Batch Processing: Process individual files or entire directories
• Smart Compression: Uses iterative compression and scaling to achieve target sizes
• Multiple Format Support: JPEG, PNG, GIF, BMP, WebP

Usage

Basic Commands

Resize a single image to under 100KB:

image-resizer -i photo.jpg -s 100

Resize all images in a directory to under 500KB:

image-resizer -i /path/to/images -s 500

Resize to specific dimensions:

image-resizer -i photo.jpg -d 800x600

Combine size and dimension constraints:

image-resizer -i photo.jpg -s 200 -d 1024x768

Maintain aspect ratio when resizing:

image-resizer -i photo.jpg -d 800x600 -r

Specify output directory:

image-resizer -i input_dir -s 100 -o output_dir

Command Line Options

• -i, --input <PATH> - Input image file or directory (required)
• -s, --size <KB> - Target file size in kilobytes
• -d, --dimensions <WIDTHxHEIGHT> - Target dimensions (e.g., 800x600)
• -o, --output <DIR> - Output directory (default: creates 'resized' subdirectory)
• -r, --maintain-ratio - Maintain aspect ratio when resizing
• -h, --help - Print help information
• -V, --version - Print version information

How It Works

File Size Reduction Algorithm

1. Quality Reduction: First tries to reduce file size by lowering JPEG quality (95% → 20%)
2. Image Scaling: If quality reduction isn't enough, starts scaling down the image by 10% increments
3. Iterative Process: Continues until the target size is achieved or maximum iterations reached
4. Best Fit: Saves the best result that meets the size requirements

Supported Formats

• JPEG/JPG - Uses quality-based compression
• PNG - Uses compression level optimization
• GIF, BMP - Basic support
• WebP - Converted to JPEG for compression (native WebP support can be added)

Examples

Batch resize photos for web upload (max 2MB):

image-resizer -i vacation_photos/ -s 2048 -o web_ready/

Prepare thumbnails (200x200, max 50KB):

image-resizer -i products/ -d 200x200 -s 50 -r -o thumbnails/

Process a single large photo for email:

image-resizer -i DSC_0001.jpg -s 500 -d 1920x1080 -r

Output

The tool provides feedback for each processed image:

Found 3 image(s) to process
✓ Processed: photo1.jpg (3456 KB → 98 KB)
  → Compressed with quality 75 to meet size target
✓ Processed: photo2.png (2100 KB → 95 KB)
  → Scaled to 85% with quality 80 to meet size target
✓ Processed: photo3.jpg (5200 KB → 99 KB)
  → Scaled to 70% with quality 85 to meet size target

Tips

1. PNG Files: PNG compression is less flexible than JPEG. For strict size requirements, consider converting to JPEG
2. Quality vs Size: The tool prioritizes meeting size requirements over maintaining quality
3. Aspect Ratio: Use -r flag to prevent image distortion when resizing
4. Large Reductions: For very large size reductions (e.g., 10MB → 100KB), expect significant quality loss

Future Enhancements

Consider adding:

• Progress bars for batch processing (using indicatif crate)
• Better WebP support (using webp crate)
• Configuration file support
• Parallel processing for faster batch operations
• Custom quality ranges
• EXIF data preservation options