Resizer

A CLI tool to compress images to fit under a target size in KB by adjusting quality and downscaling if needed.

Installation

Clone the repository and build with Cargo:

git clone <repository-url>
cd resizer
cargo build --release

The binary will be available at target/release/resizer.

Usage

resizer [OPTIONS] <input> <output>

Options

• --target-kb <TARGET_KB>: Target size in KB (upper bound)
• --format <FORMAT>: Output format: jpeg, webp, or png [default: webp]
• --max-width <MAX_WIDTH>: Optional max width
• --max-height <MAX_HEIGHT>: Optional max height
• --min-quality <MIN_QUALITY>: Min quality (1..=100) [default: 30]
• --max-quality <MAX_QUALITY>: Max quality (1..=100) [default: 95]
• --max-downscale-rounds <MAX_DOWNSCALE_ROUNDS>: How many downscale rounds to attempt [default: 10]
• --png-compression-level <PNG_COMPRESSION_LEVEL>: PNG compression level (0-9, higher = slower but smaller) [default: 6]
• --help: Print help

Examples

Compress an image to under 100 KB as WebP:

resizer input.jpg output.webp --target-kb 100

Compress with max dimensions and PNG format:

resizer input.png output.png --target-kb 50 --format png --max-width 800 --max-height 600 --png-compression-level 9

Behavior

• For JPEG and WebP: Uses binary search on quality to find the highest quality that fits the target size. If min quality still exceeds the target, downscales the image by 10% and retries. Pre-downscaling is applied for very large images.
• For PNG: No quality search; encodes at the specified compression level. If too large, downscales by 10% and retries.
• JPEG converts to RGB (transparent pixels become black).
• WebP preserves alpha if present.
• PNG preserves alpha if present.

License

MIT License - see LICENSE file.