![]() Hockenberry said there’s a difference in how error diffuses-Atkinson dithering is serpentine, alternating direction line by line, while Apple’s implementation isn’t. (Atkinson installed BitCam and told me the dithering isn’t identical to his eponymous version. īill Atkinson, photographer and one of the original members of the Apple Macintosh development team.Ītkinson said via an email interview, referring to the way the algorithm alternates direction in processing lines of pixels from the original, “Turns out when you are propagating right and down, the left and down propagation is essential to break up standing waves that create ugly streaking rivulets.” He noted that to create the QuickDraw dithering routine, he wrote a program that tested many different weighted variations of standard dithers, and picked the one generated the most pleasing result. Think of it as an analog to image feathering, where an edge is turned from sharp and jagged to smooth. The rounding errors of conversion have to be diffused into surrounding areas, but precisely in which directions and how far they ripple outward will dramatically affect the resulting image. The classic Atkinson dither was originally used to convert grayscale and color images and some graphics into 1-bit bitmaps.Ītkinson tweaked older dithering routines to improve the mid-tone areas in order to avoid discontinuity. In image processing, dithering takes a tonal value and converts it into a concentration of dots that fools the eye into interpreting the approximate shade. It accurately reproduces the look and feel of a 1984-style Macintosh app down to using a similar dithering algorithm to what Bill Atkinson baked into the graphics-primitive QuickDraw system that drove the graphical user interface and drawing programs-and that’s now also baked into iOS (part of its Accelerate framework).ĭithering is a technique that allows conversion from a higher-resolution form to a lower-resolution one by introducing noise to override the “quantization error,” which results otherwise in visible bands and artifacts in images and extraneous or distracting tones in music. The Iconfactory’s newīitCam, a nostalgic dithered camera app, would at first seem to be another filter and just a gimmick. I see many fewer artificially aged or worn pictures these days, and the range of filters has expanded into a greater array of interesting photographic effects. We remember the past as slightly faded, orange-tinged photos, and Instagram and others provide a taste of that sense. Taking pictures with increasingly better modern phones’ cameras and then rubbing digital dirt on them and leaving them virtually out in the simulated sun always seemed to me to be about the conflict between stark perfection and the quality of memory. I’ve always had a problem with retro camera filters.
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