How Does Image Optimizer Pro Work?
Image Optimizer Pro combines two compression engines for the best results across all image formats:
- pngquant (WASM) — For PNG output, the tool uses libimagequant compiled to WebAssembly. This is the same engine behind the popular pngquant command-line tool. It reduces PNG images from millions of colors to a 256-color palette, achieving 60-80% file size reduction while maintaining excellent visual quality.
- Canvas API — For JPEG and WebP output, the tool uses the browser's built-in Canvas API with configurable quality settings. This provides reliable, fast compression for photographic images.
Supported Formats
Image Optimizer Pro accepts images in multiple formats:
- PNG — Re-quantize existing PNGs for smaller file sizes using pngquant.
- JPEG — Compress with adjustable quality or convert to other formats.
- WebP — Compress or convert WebP images.
- GIF — Convert GIF frames to optimized output (first frame).
- BMP — Convert uncompressed bitmaps to compact optimized output.
- AVIF — Convert AVIF images (browser support required).
Understanding the Controls
PNG Output (pngquant)
- Quality Min/Max — Sets the acceptable quality range (0-100). The optimizer uses the fewest colors possible while staying within this range. Max 80 with min 0 works well for most images.
- Max Colors — Limits the palette size (2-256). Fewer colors means smaller files but more visible banding.
- Speed — Trade quality for processing speed (1-10). Speed 1 produces the best results but takes longer.
JPEG/WebP Output (Canvas API)
- Quality — Controls lossy compression level (10-100%). 70-85% is recommended for web use. Higher values preserve more detail at larger file sizes.
When to Use Each Format
- PNG — Screenshots, UI graphics, icons, logos, charts, and images with text or sharp edges. Best when you need transparency.
- JPEG — Photographs and images with smooth gradients. No transparency support.
- WebP — Modern format, typically 25-35% smaller than JPEG at equivalent quality. Supported by all modern browsers. Best choice for web images.
- Keep Original — Optimizes each image in its original format. PNG/GIF/BMP use pngquant, JPEG/WebP use Canvas API.
Frequently Asked Questions
Is my data uploaded to a server?
No. Everything runs locally in your browser using WebAssembly and the Canvas API. Your images never leave your device.
Can I upload multiple files at once?
Yes. You can drag and drop or select multiple files. They will all be processed with the current settings. Use "Re-optimize All" to reprocess after changing settings.
Why is the compressed file sometimes larger?
This can happen when converting between formats (e.g., JPEG to PNG) or when the original image is already well-optimized. Try a different output format or lower quality settings.
Does this preserve image metadata (EXIF)?
No. Both compression methods strip EXIF metadata. This is a privacy benefit for images you plan to share, but use a dedicated tool if you need to preserve metadata.