ImageOptim is a front-end (GUI) for set of tools for optimisation of PNG and JPEG images.
Optimization makes files smaller (in terms of disk space) by finding optimal compression parameters and by removing unnecessary information, like file comments, EXIF tags, and color profiles.
Note: While the software is classified as free, it is actually donationware. Please consider making a donation to help support development.
Another fix for grayed-out menu items