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From: jef@ace.ee.lbl.gov (Jef Poskanzer)
Newsgroups: comp.graphics
Subject: Re: 8x8 dither matrices
Message-ID: <2518@helios.ee.lbl.gov>
Date: 30 Apr 89 21:23:57 GMT
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Reply-To: Jef Poskanzer <jef@helios.ee.lbl.gov>
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In the referenced message, daveb@cbmvax.UUCP (Dave Berezowski) wrote:
}                                                 I now know how to generate
}ordered dither matrices of size power's of 2(ie. 2, 4, 8, etc.) BUT am
}still looking for references on Halftone dither matrices above a 4x4.

I'm not completely sure what you mean by "Halftone".  Halftoning is
the generic term for any sort of N-bit to 1-bit quantization.  (Terminology
is great, isn't it?)  Anyway, assuming you are talking about clustered
dithering of the sort used in newspaper photographs, here is an order-8
45-degree clustered dither matrix:

    static int cluster8[8][16] = {
	 65, 70, 78, 88, 87, 77, 69, 68, 64, 59, 51, 41, 42, 52, 60, 61,
	 71, 95,101,110,109,100, 94, 76, 58, 34, 28, 19, 20, 29, 35, 53,
	 79,102,115,117,116,113, 99, 84, 50, 27, 14, 12, 13, 16, 30, 45,
	 89,111,124,125,126,119,108, 86, 40, 18,  5,  4,  3, 10, 21, 43,
	 90,112,123,128,127,118,107, 85, 39, 17,  6,  1,  2, 11, 22, 44,
	 80,103,120,122,121,114, 98, 83, 49, 26,  9,  7,  8, 15, 31, 46,
	 72, 96,104,105,106, 97, 93, 75, 57, 33, 25, 24, 23, 32, 36, 54,
	 66, 73, 81, 91, 92, 82, 74, 67, 63, 56, 48, 38, 37, 47, 55, 62 };

The only reference you need for this stuff is "Digital Halftoning" by
Robert Ulichney, MIT Press, ISBN 0-262-21009-6.
---
Jef

            Jef Poskanzer   jef@helios.ee.lbl.gov   ...well!pokey
 "Wild geese have no intent to cast reflections; water has no mind to receive
                                their image."