The GIF images below and on the next page compare common image optimization strategies, demonstrating the benefits of the WebScrub algorithm. View in both 8-bit (256) color mode and higher depths to compare quality, then note the file size differences. The gains are often modest in individual cases, but because the scripts can easily be worked into batch production processes, the net benefit can be significant.


44,878 bytes. This is an 8-bit pre-dithered GIF - the highest visual quality and worst compression.

26,602 bytes. This is pre-dithered to "the web palette." It looks like this at all color depths. Regrettably, much "conventional wisdom" has it that this is the best strategy for all GIFs.

21,446 bytes. This is indexed with no dithering to the web palette. It looks sickly at all color depths. Other, more colorful images would suffer more from this treatment.

19,006 bytes. This is dithered to a 4-bit adaptive palette. It will appear dithered in all viewing situations, and "double-dithered" at 8-bit, fatal to some images.

18,026 bytes. This is indexed to a 4-bit adaptive palette with no (pre) dithering. It still appears dithered in 8-bit viewing situations.

18,026 bytes. This is the preceding image after processing with the WebScrub plug-in, with a "grit" setting of 30. It appears only minimally dithered in 8-bit viewing situations, with better contrast at all depths.

16,150 bytes. A token JPEG version, compressed to comparable size, just to show the trade-offs of this approach.
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