ImageOptim decreases the file size of PNG, JPEG, and GIF images, even those "Saved for Web". It combines OptiPNG, PNGCrush, AdvanceComp, PNGOUT, Jpegoptim + Jpegtran, and Gifsicle for the best possible optimization.
Pngtastic reduces the filesize of PNG images without sacrificing image quality. It runs on the command line or via the included ant task. Pngtastic makes integrating PNG image optimization into your Java build process easy.