RIOT 1.0.7

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.

Note: We've detected that RIOT's installer might attempt to bundle third-party software. We suggest to proceed with caution and select the "Custom" installation option to identify any potential unwanted software.
1.9 MB
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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.


  • 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)

What's New:

  • added automatic optimization mode
  • added loading support for "half float" format to TIFF
  • added drag folder to load files in batch mode
  • added progress monitoring for jpeg load/save and resize
  • superior internal PNG compression. Added 4 compression levels (zlib-9 with heuristics and filters for low setting and zopfli deflate used for the higher settings)
  • color quantization to 2 colors now outputs 1 bit images instead of 4 bit (smaller filesize)
  • changed transparency settings (added simplify checkbox)
  • faster color quantization of images with 16 colors or less (output bit depth controlled by the quantizer itself)
  • greatly improved resize/resampling speed
  • upgraded to LibTiff 4.0.3
  • upgraded to libPNG 1.5.13
  • upgraded to OpenJPEG 1.5.1
  • allowed loading of PNG with benign errors (such as images with too many IDATs)
  • batch settings: keep date date & report size changes options are now preserved
  • fixed crashing when loading some JPEG files with invalid EXIF tag length
  • fixed PNG plugin with saving of transparent monochrome images
  • fixed JPEG error: Exif: Suspicious offset of first IFD value
  • fixed a crash when loading TIFF images with a TIFFTAG_TRANSFERFUNCTION Exif tag
  • fixed a crash reading a TIFF with an uncommon 24-bit palettized file
  • allowed loading of TIF with missing bitspersample/samplesperpixel/photometric tags
  • fixed BigTIFF signature validation
  • fixed TIFF plugin truncating metadata tag on loading if type is ASCII and it's value is of variable size (TIFF_VARIABLE)
  • fixed loading of Exif with bad thumbnail data or with a bad first offset size
  • fixed PSD parser when reading PSD files with corrupted resources
  • resize: fixed a NULL-pointer access bug occurring for transparent images with a linear palette
  • removed PNG interlacing
  • removed Grayscale from Color reduction presets => replaced with Grayscale checkbox in Image adjustments
  • removed libMNG, using internal reader instead