What are some alternatives?
ImageOptim - Faster web pages and apps.
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
WP Smush - Reduce image file sizes, improve performance and boost your SEO using the free WPMU DEV WordPress...
PNGGauntlet - -Combines PNGOUT, OptiPNG, and DeflOpt to create the smallest PNGs
way2enjoy - Try image Optimizer. Compress and optimize image,PDF,MP3 by w2e image compressor. Resize image, compress image by lossy/lossless image optimization.