ImageOptim is described as 'Is excellent for publishing images on the web (easily shrinks images “Saved for Web” in Photoshop). It's useful for making Mac and iPhone/iPad applications smaller (if you configure Xcode to allow better optimization)' and is a popular Image Optimizer in the photos & graphics category. There are more than 100 alternatives to ImageOptim for a variety of platforms, including Windows, Web-based, Mac, Linux and Wordpress apps. The best ImageOptim alternative is ImageMagick, which is both free and Open Source. Other great apps like ImageOptim are Caesium Image Compressor, FileOptimizer, OptiImage and TinyFast.
ImageOptim alternatives are mainly Image Optimizers, but if you're looking for
File Compressors or Image Converters you can filter on that. Other popular filters include
Windows. These are just examples - use the filter bar below to find more specific alternatives to ImageOptim.