Path: utzoo!attcan!uunet!husc6!cmcl2!polyof!pickel
From: pickel@polyof.UUCP ( Prof. Pickel )
Newsgroups: comp.graphics
Subject: Re: RGB -> CMY -> hardcopy
Summary: experience with color plotters
Keywords: RGB,CMY,printer,halftoning
Message-ID: <373@polyof.UUCP>
Date: 7 Sep 88 19:03:17 GMT
References: <23632@hi.unm.edu>
Organization: Polytechnic University, Farmingdale NY
Lines: 27

In article <23632@hi.unm.edu>, cyrus@hi.unm.edu (Tait Cyrus) writes:
> 
> I am working on a utility that takes an RGB image (3 files, 1 for R, 1
> for G and 1 for B), converts it halftones, and then converts it to CMY
> so that I can print it on a color CMYB versatec printer we have.
> 
> My problem is that the colors don't seem to be coming out looking
> correct.  Cyan comes out looking blue, blue comes out looking purple,
> green comes out too dark, etc.....
we have been working on 512 by 512 by 8bits RGB to 2560 by 2560 CYMB
for a shinko thermal tranfer plotter

there is a major difference in the colors printed depending on the
rate at which the data is sent to the plotter

at slower speeds it was necessary to shift the RGB to get more
saturated colors

at the highest speed straight C = 255 - R etc Black = min CYM
seems to work quite well (followed by ordered dither)

currently we use a sharpened gaussian filter to go from 512 to 2560

total processing time for each picture is about 27 minutes on a VAX
class machine (16 min CPU)

I'm working on faster approaches.