FileOptimizer is a tool which aims to reduce the size of many common file types (AIR, APK, APNG APPX, BMP, CBZ, DOCX, DLL, EPUB, EXE, GIF, GZ, ICO, JAR, JPEG, MNG, MP3, MPP, PNG, PPTX, ODT, OGG, OGV, PDF, PUB, SCR, SWF, TIF, VSD, WEBP, XAP, XLSX, and ZIP) while keeping their functionality and appearance untouched.
And so the idea is that your JPEG images (for instance) will look exactly the same; they'll just be smaller than they were before.
To use the program, you first drag and drop your files onto the interface. Right-click the image, choose Optimize, and it'll call up one of a host of compression tools to do the actual work (essentially it's just a front end for various other free and open source apps). The "before" and "after" file sizes are displayed, so you can inspect the results right away.
While this sounds very appealing, one immediate problem with FileOptimizer is that it doesn't always work. Some of our more complex test source files (executables, archives) were effectively corrupted by the compression process, rendered entirely unusable.
And another complication is that FileOptimizer automatically replaces your original files with the compressed versions, obviously an issue if they're now corrupted. You can recover the originals from the Recycle Bin, but of course if you get distracted by some other issue it's possible that you might forget, accidentally empty the Bin and lose them.
Still, most of the time FileOptimizer works extremely well, and in the main we found it produced excellent results (some PNG and PDF files were compressed by around 50%, for instance). Just use it with extreme care: work with copies of files, not the originals, and check them carefully to confirm that they still work precisely as they did.