PNG file optimizer
Download from PortableApps.com
PngOptimizer Portable can run from a cloud folder, external drive, or local folder without installing into Windows. It's even better with the PortableApps.com Platform for easy installs and automatic updates.
PngOptimizer cleans your PNG files of useless or wrong information. Reduces your PNG files weight. Converts into PNG other lossless image formats (BMP, GIF, TGA). Supports animated PNG (APNG). Creates easily available PNG screenshots. Offers a simple and productive user interface. Both the 32-bit and 64-bit version are included and the correct one automatically selected for best performance. Note that it will not currently run on Windows XP 64-bit.