Crunch is a macOS 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 embedded versions of the pngquant and zopflipng PNG optimization tools.
The example images are impressive. Obviously, you won’t want to use this on your archival or source images. I did a quick test on a few of sites at work, and was able to take some PNGs w/ transparent backgrounds down from 1.5mb to 130kb. That’s a greater than 10x reduction in size. Jimminy.