PUBLIC MARKS from Spone with tags png & optimisation

Kraken is a robust, ultra-fast image optimizer and compressor with best-in-class algorithms. We'll save you bandwidth and storage space and will dramatically improve your website’s load times.

pngquant is a command-line utility and a library for converting 24/32-bit PNG images to paletted (8-bit) PNGs. The conversion reduces file sizes significantly (often as much as 70%) and preserves full alpha transparency. Generated images are compatible with all modern web browsers, and have better fallback in IE6 than 24-bit PNGs.

Advanced lossy compression for PNG images that preserves full alpha transparency.