There are many file optimisation utilities available. These make files smaller in a lossless manner, typically by decompressing their internal elements and recompressing them using a compression algorithm with a higher compression ratio at the expensive of processing time. Using these can be tricky though - finding the right utility, checking against accidential corruption. What of files contained within other file container? Minuimus solves this: It's an automation wrapper.
Just point minuimus.pl at your data, and watch it shrink - and shrink in a manner which is completely transparent. Your image files will get smaller, and not a pixel will change in value. Minuimus supports png (including animated png extension), jpeg, gif, zip, epub, docx, xlsx, jar and pdf. Unrecognised file extensions will be skipped.
Minuimus goes beyond just calling on AdvanceCOMP. When faced with files which are zip containers - such as zip, epub, or docx - it will extract these files, recursively process all of the files contained within them, and put them back together. In this manner it can make e-books and office documents substantially smaller.
Use it to make your website faster, your game easier to distribute, or just to squeeze more pointless holiday photographs on to your computer. It's written on ubuntu linux, but should be adaptable to other distributions.
Exactly what minuimus.pl does depends upon the file: