Images can start to take up a lot of disk space, but with ImageOptim you can cut them down to size without losing quality.
ImageOptim has an extremely simple interface, which features a number of open source optimization tools under the hood. There is AdvPNG from AdvanceCOMP, OptiPNG, Pngcrush, JpegOptim, jpegtran from libjpeg, Gifsicle and you can add PNGOU too. This means ImageOptim is compatible with PNG, JPEG and GIF animations.
We tested a range of images, and the results are good. You can often save 20-30% of the size without losing any image quality. With a large collection of images this can be significant.
ImageOptim is ideal for image you want to upload to web pages, as it improves load times. It's worth noting that ImageOptim changes the original file: if you are worried about losing originals, make sure to only optimize copies!
If you're looking for a no-nonsense way to shrink image size, ImageOptim is ideal. It's really easy to use and gives impressive results.