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FAQ: What are the ArcPress dither patterns and how are they used?

Question

What are the ArcPress dither patterns and how are they used?

Answer

Dithering expands the perceived range of a color palette. Using the native primary colors on a raster output device, dithering arranges adjacent printer dots (pixels) in patterns to create the illusion of other colors. ArcPress uses two types of dithering: blue noise random dither and ordered dither.

Blue noise random dither: This is an error diffusion where the color error and pixel placement is randomly distributed over the image. ArcPress offers eight blue noise dithers:

· blue - Floyd & Steinberg (1975). This is the default.
· blue2 - Jarvis, Judice & Ninke (1976)
· blue3 - Stucki (1981)
· blue4 - combination Floyd & Steinberg and Stucki
· blue5 - combination Jarvis et al. and Stucki
· blue6 - combination Floyd & Steinberg and Jarvis et al.
· blue7 - combination Stucki and Floyd & Steinberg
· blue8 - combination Stucki and Jarvis et al.

Ordered dither: This is an error diffusion where the color error and pixel placement is distributed as a 90 degree angle matrix—left to right, and top to bottom.

How to select the dither pattern: Depending on the colors, particularly the adjacent colors on your map, some of the dithering algorithms may produce better results. If you are dissatisfied with the default, try blue2 or blue4 and then the others.

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