PNGOptimizer is a portable tool that will strip your PNG files of useless or incorrect information, thereby making the filesize of your PNG images smaller. PNGOptimizer can also convert GIF, BMP or TGA image files to optimized PNG images. Moreover, it can be used to automatically create optimized PNG images from screenshots captured via the print screen key.
PNG Optimizer Screenshot
Authors Website: http://psydk.org/pngoptimizer
License: Open Source
Download: Get this PNG Conversion and Optimizing Tool HERE