What are some alternatives?
Imagify - Optimize and resize images online and through your CMS.
ImageOptim - Faster web pages and apps.
way2enjoy - Try image Optimizer. Compress and optimize image,PDF,MP3 by w2e image compressor. Resize image, compress image by lossy/lossless image optimization.
OptiPNG - OptiPNG is a command-line PNG optimizer that recompresses image files to a smaller size, without...
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
pngquant - command-line utility and library for lossy compression of PNG images