What are some alternatives?
Lepton - Lepton image compression: saving 22% losslessly from images at 15MB/s
ImageOptim - Faster web pages and apps.
File Converter - Convert & compress everything in 2 clicks!
pngquant - command-line utility and library for lossy compression of PNG images
PNGGauntlet - -Combines PNGOUT, OptiPNG, and DeflOpt to create the smallest PNGs
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.