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:

  • Replaced AVX2 with SSE2 for better compatibility with older CPUs
  • 64 bit version, allowing bigger images to be processed (>50 MP)
  • Improved compression with up to 30% for jpeg images
  • Decoding support for jpeg images using arithmetic coding
  • Improved PE security with DEP and ASLR
  • The AVX2 instruction set for the 64bit version should provide better performance on larger images
  • The 32 bit version is gonna be deprecated (probably the last 32 bit release)
  • Fixed display of optiized size in higher text dpi settings
  • Using less memory after the image is analyzed
  • Other minor fixes & tweaks