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From: daveb@cbmvax.UUCP (Dave Berezowski)
Newsgroups: comp.graphics
Subject: Re: 8x8 dither matrices
Message-ID: <6717@cbmvax.UUCP>
Date: 30 Apr 89 17:19:31 GMT
References: <6663@cbmvax.UUCP> <5040008@hpfcdc.HP.COM>
Reply-To: daveb@cbmvax.UUCP (Dave Berezowski)
Organization: Commodore Technology, West Chester, PA
Lines: 36

In article <5040008@hpfcdc.HP.COM> bayes@hpfcdc.HP.COM (Scott Bayes) writes:
>A common way of enlarging a 4x4 matrix to 8x8 is:
>
>multiply the matrix by the scalar 4.
>
>tile the 8x8 matrix with 4 copies of the scaled-up 4x4 matrix
>
>add the constant 1-matrix  	1 1 1 1
>				1 1 1 1
>				1 1 1 1
>				1 1 1 1
>
>to the upper right-hand tile. Add the constant 2-matrix to the lower left tile,
>and add the constant 3-matrix to the lower right tile (actually you also add
>the constant 0-matrix to the upper left tile). This produces an 8x8 matrix
>that is fractally similar to the 4x4 starter, and shares many of its noise
>distribution properties.
>
>It can be applied to any 2^n by 2^n. For example n=0:
>
>matrix = 0
>
>Deriving the next up (n=1):
>
>matrix =0 1
>        2 3
>
>etc.
>
>Scott Bayes
>dithering as usual

	An interesting trick which works fine on Ordered dither matrices,
but does not work for Halftone dither matrices.  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.