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The free and portable Radical Image Optimization Tool (RIOT) has been an app I’ve recommended for a few years now (I think I’ve been using it since about 2008). As the name suggests it focuses on doing one thing, and doing it well: optimizing images. It can compress, resize, adjust, and convert your images in a way that leaves you in control of the end result.

The thing I like the most about riot is how easily I can manipulate multiple photos in just a few clicks. Thanks to the “batch” button on the toolbar I can select an entire folder of images that I want to resize and/or compress, and the speed at which it can process the images is rather incredible. This is great for emailing off a slew of photos when you’re concerned about the attachment size.

Most of the time I use RIOT for batch optimizations, but this regularly-updated app is equipped with all kinds of other 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).
  • 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
  • Resize image by using well known resample filters (ex: Lanczos3, Catmull Rom, Bicubic, and others)
  • Compression and the results are comparable to those of commercial products, even higher.
  • Adaptive logarithmic tone mapping algorithm (Drago) used for HDR images

Seeing that RIOT is free and portable you can give it a try without much worry. I highly recommend keeping this one in your toolbox.

RIOT Homepage (Windows only; Freeware/Portable)