PunyPNG : PunyPNG is a free website optimization tool that dramatically reduces the file size of your images without any loss of quality.
Trimage (lossless) image compressor : Trimage is a cross-platform GUI and command-line interface to optimize image files via optipng, pngcrush, advpng and jpegoptim
Squoosh : Squoosh is an image compression web app that allows you to dive into the advanced options provided by various image compressors.
Pngcrush : Pngcrush is an optimizer for PNG (Portable Network Graphics) files. It can be run from a commandline in an MSDOS window, or from a UNIX or LINUX comma...
CSS Sprite Generator : This tool allows you to automate the process of generating CSS sprites. Simply give it a ZIP file containing 2 or more images (GIF, PNG or JPG) and it...
Crunch is a tool for lossy PNG image file optimization. It combines selective bit depth, color type, and color palette reduction with zopfli DEFLATE compression algorithm encoding using the pngquant and zopflipng PNG optimization tools.