What are some alternatives?
ImageOptim - Faster web pages and apps.
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
WP Smush - Reduce image file sizes, improve performance and boost your SEO using the free WPMU DEV WordPress...
Optimus.io - Lossless image optimization