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)

Optimization details
JPEG settings
You can find the following JPEG settings:
* quality (compression)
* advanced chroma subsampling (none,low 4:2:2,medium 4:2:0,high 4:1:1)
* save as 8bit grayscale
* standard optimized (optimal Huffman tables) or progressive encoding

Supported output bit depths: 24 bit color, 8 bit grayscale

GIF settings
The following GIF settings are currently implemented:
* color reduction
o color quantization downto 256..2 colors (no dithering) using Xiaolin Wu or NeuQuant neural net
o grayscale 8bit palette
o floyd-steinberg dithered 1bit monochrome
* save interlaced
Supported output bit depths: 4, 8 bit color, 8 bit grayscale, 1 bit monochrome

PNG settings
The following PNG settings are currently implemented:
* true color support (24 bit RGB, 32 bit RGBA)
* color reduction
o color quantization downto 256..2 colors (no dithering) using Xiaolin Wu or NeuQuant neural net
o grayscale 8bit palette
o floyd-steinberg dithered 1bit monochrome
* save interlaced
* maximum compression setting using internal heuristics
* out-of-the-box integration with popular PNG optimizers (optiPNG, PNGOut)
o add/remove/modify external PNG optimization tool
Supported output bit depths: 4, 8, 24, 32 bit color, 8 bit grayscale,1 bit monochrome

Metadata settings
Choose to keep or remove the following metadata:
* comments
* Adobe XMP info
* IPTC info
* EXIF profile (including GPS and maker notes)
* ICC color profiles
Unknown or unsupported metadata is automatically removed.