What are some alternatives?
XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
ImageOptim - Faster web pages and apps.
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
Converseen - Converseen is a cross-platform image processing software that converts image file formats. Converseen does this by resizing, renaming and reshaping images. Read more about Converseen.
PNGGauntlet - -Combines PNGOUT, OptiPNG, and DeflOpt to create the smallest PNGs