HyperDither is an OS X image processing utility that converts color or grayscale images to 1-bit black-and-white using a sophisticated dithering routine. Specifically, HyperDither implements the “Atkinson” dithering matrix.


Years ago, during the development of the first Macintosh, Bill Atkinson (of HyperCard, QuickDraw, MacPaint, and now nature photography fame) discovered a very elegant dithering filter to convert greyscale image data for the 1-bit black-and-white Mac video display. The dithering produced by this routine was much higher in quality than the now-ubiquitous Floyd-Steinberg or “error-diffusion” filter (used by QuickTime, Photoshop).

The dither routine was implemented as an option in Apple’s long-gone HyperScan software (A HyperCard stack with some XCMDs/XFCNs) that would connect an early Mac to a flatbed scanner. HyperScan, and hence the most-excellent Atkinson dithering routine, has been unavailable for many, many years—but not forgotten! I e-mailed Bill Atkinson in January, 2003, and inquired about the details of the algorithm. He was kind enough to respond with a brief write-up of the routine.



To process an image with HyperDither, just drag and drop or copy and paste the image into HyperDither’s main window. You can then save it to disk or copy it back to the clipboard.

To batch-process a folder of images, just drag the folder into HyperDither’s main window:




HyperDither is free!

System Requirements

HyperDither 1.3 was developed on OS X 10.5.2—systems back to OS X 10.3 should work, but have not been tested. HyperDither is a Universal application, which means it will run natively on PowerPC and Intel Macs.


A page of examples can be found here, as well as a series of comparisons between HyperDither and Photoshop dithering.

The types of images that tend to look best have high contrast. Incidentally, the original implementation of the algorithm intentionally increased the contrast of the final images (which also made them faster to compute). HyperDither lets you choose between high-contrast and no-contrast adjustments, and gives the option of adding a sharpening pass.

Current Version

1.3 Universal (Intel & PowerPC)

What’s New In This Version?
  • 12.5%, 25% & 50% reduced views.
  • Optimized PNG export—tiny, loss-less files!
  • Several redraw bugs related to the view menu have been fixed.

A Read Me file with a complete change log can be found in the download archive.

zip HyperDither 1.3
(65535 downloads since 2011-01-23)