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From: bzs@bu-cs.BU.EDU (Barry Shein)
Newsgroups: comp.windows.x,comp.graphics
Subject: 4x4 Dithering Patterns?
Message-ID: <31971@bu-cs.BU.EDU>
Date: 30 May 89 02:40:26 GMT
Organization: Boston U. Comp. Sci.
Lines: 29


First, does anyone have a set of 4x4 dithering patterns for
pseudo-halftone? If so perhaps you could mail it to me (should be
fairly small, just an array of hexnums or some such, I'll figure
it out.)

Second, after having tried to create my own it strikes me that either
I am dense (ahem) or, in general, there's no obvious way to create
such patterns. In part one could chalk it all up to a matter of taste
(and application) but is there more guidance than I suspect?

For a 4x4 dither there are 32,768 possible patterns, that's too many
to just skim through with a tool. One can eliminate a lot of them with
some easy tests (eg. anything stripey is not a candidate, such as
0xf0f0). Then I guess you could sort them roughly by the percentage of
bits set, the intensities will more or less fall along those lines.

Beyond that I have no idea for an algorithmic way to choose even
high-probability dithers (eg. narrow down to a few choices in a range
and then just look at a tiling of them.)

Is there more order than I describe here? Perhaps I should have gone
to the library first and sorted through papers but perhaps someone on
this list will point me towards some and save me some time.
-- 
	-Barry Shein

Software Tool & Die, Purveyors to the Trade
1330 Beacon Street, Brookline, MA 02146, (617) 739-0202