PNGGauntlet is a simple but handy application that enables you to compress and optimize images in a few steps.
The program features a nice and intuitive user interface, very customizable and easy to use. To compress any file you just need to add it, select the output directory, the compression strategy,and press optimize. It compresses many formats, optimizes PNG files, and even converts BMP, TGA, JPG, GIF, and PCX files to PNG. The program five compression levels varying from Xtreme (slowest) to uncompressed (fastest). You can also select bit depth, color type, and filter type, as well as other more advanced options which include block split, buggy decoder mode, chunks to keep and others. One of the main uses of this program is to compress images that are going to be uploaded to websites, since it makes it lighter and helps decrease bandwidth costs. You can leave the program compressing files while you do other things, but it doesn't offer the options to pause and resume compressions, and you cannot compress an entire folder. However, the advantage is that it is completely free.