What are some alternatives?
ImageOptim - Faster web pages and apps.
Image Tuner - Image Tuner is a free software for batch resizing, converting, watermarking and renaming your...
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists
GraphicsMagick - GraphicsMagick is the swiss army knife of image processing.