Path: utzoo!attcan!uunet!husc6!mailrus!ames!pacbell!att!alberta!oha!tony From: tony@oha.UUCP (Tony Olekshy) Newsgroups: comp.lang.postscript Subject: Re: Screening Procedures Summary: How can you prevent halftoning from repeating the pattern? Keywords: PostScript random halftone screen Message-ID: <248@oha.UUCP> Date: 2 Jul 88 00:14:57 GMT References: <174@chip.UUCP> Organization: Olekshy Hoover & Associates Ltd., Edmonton,Alberta,Canada Lines: 22 In , sg1q+@andrew.cmu.edu (Simon Peter Gatrall) writes: > > I've been interested in playing with the procedures PostScript uses to do > halftoning, and I was wondering if anyone else is familiar with this stuff. > One thing that bothers me is that once a pattern is made to represent a > specific gray value, it isn't recomputed. This makes all the sense in the > world for line and dot screens, but what if you want something that looks > like a texture? Here, here! The following code will generate a random-patterned grey scale with the probability of any pixel being white being proportional to the grey level: 1 45 { pop pop rand 1073741824 div 1 sub } setscreen The problem is that when you use this, the maximum area that gets patterned is 0.1" x 0.1", and THAT pattern is replicated over the whole area being painted. CAN halftoning be used to randomly pattern the entire area being painted? Yours, etc., Tony Olekshy (!alberta!oha!tony, +1 403 425 9657).