Radical Image Optimization Tool (RIOT for short) is a free image optimizer that will let you to visually adjust compression parameters while keeping minimum filesize.
It uses with a side by side (dual view) or single view interface to compare the original with the optimized image in real time and instantly see the resulting file size.
It is lightweight, fast and simple to use, yet powerful for advanced users. You will be able to control compression, number of colors, metadata settings and much more, and select image format (JPG, GIF or PNG) for your output file.
* fixed a bug with Paste from clipboard. Pasted images were shifted a few pixels.
* fixed a bug in the DLL version with the toolbar containing rotate, resize, compress to size, etc.
The toolbar should be enabled after successful image loading from the host application.
Product page: here