RIOT v0.5.2

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.

The image optimizer 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 (JPEG, GIF or PNG) for your output file.

RIOT can be integrated as plug-in in well known programs like The GIMP, IrfanView and XnView

Main features:

open many image types including rare/scientific types

save and optimize JPEG, GIF and PNG with a simple, clean user interface

works in dual view: (original – optimized image) or single view (optimized image).

Automatic preview of resulting image

in-place compare function (alternativelly display the original image over the optimized image to notice small pixel changes)

compress files to desired filesize threshold

fast processing (all is done in memory);
see instant results including resulting filesize

batch support (process multiple files at once)

transparency handling options

decide if you want to keep metadata (comments, IPTC, Adobe XMP, EXIF profiles, ICC profiles).

Unsupported metadata is removed

transfer metadata between image formats (destination format must support them)
common tools: pan and zoom, rotate, flip

basic image adjustments: brightness, contrast, gamma, invert

visually reduce number of unique colors for PNG and GIF images in order to reduce filesize
(two quantization methods are available: Xiaolin Wu and NeuQuant neural net)

resize image by using well known resample filters (ex: Lanczos3, Catmull Rom, Bicubic, and others)

out-of-the-box support for external PNG optimizers (optipng, pngout, etc)

the compression and the results are comparable to those of commercial products, even higher.

Adaptive logarithmic tone mapping algorithm (Drago) used for HDR images

Input image types

common bitmap images as well as Adobe Photoshop PSD files

popular HDR formats and RAW camera images

rare/scientific types (up to 128 bpp, integer and floating point)

The program is portable. No install required.