RIOT - the Radical Image Optimization Tool - is a free utility that will quickly cut your online graphics down to size, speeding up your website, reducing your bandwidth requirements, and maybe even saving you money.
A new Full Auto Mode introduced in RIO 0.5 means the program is very simple to use. Just drag and drop an image onto the left hand pane, various compression and quality settings are chosen for you, the savings in file size are displayed and RIOT's Preview window updates with the new image, ready for your approval.
If you'd like to try and squeeze a few more bytes from the image, though, there are further manual options you can try. JPEGs use two types of encoding, for instance, Standard and Progressive. Which delivers the smallest file size? Choose the appropriate option and RIOT will show you the effect on file size.
You can tweak the "Chroma subsampling" value, too, a ratio that defines how the image is encoded. Complicated? Yes, it is, but you don't need to understand how it works - just try each value in turn (there are only four) and see which one delivers the smallest possible file size.
And RIOT even allows you to apply simple tweaks to the image, for further size reductions. It can flip an image horizontally or vertically, or rotate it left or right, both of which will have a small effect on the file size.
Other sliders will adjust the picture brightness, contrast and gamma, for more significant changes. Reducing contrast will usually cut your image file size, for instance - turn it down as far as you can, without adversely affecting image quality, to save the maximum number of bytes.
Version 0.5.2 is a bug fix release.