Xref: utzoo comp.graphics:10177 comp.sys.ibm.pc.programmer:205
Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mcnc!ecsvax.uncecs.edu!cjl
From: cjl@uncecs.edu (Charles J. Lord)
Newsgroups: comp.graphics,comp.sys.ibm.pc.programmer
Subject: Re: 256 GrayScale Matching to 256 Colors
Summary: 8-bit gray - 6-bit color=2bit opinion
Keywords: Look Up Table Needed
Message-ID: <1990Mar2.043848.501@uncecs.edu>
Date: 2 Mar 90 04:38:48 GMT
References: <858@dukempd.phy.duke.edu>
Followup-To: comp.sys.ibm.pc.programmer
Organization: Triangle R&D Corp,RTP,NC
Lines: 16

It sounds possible, but the problem is that the color pallette
on the VGA is 18 bits: 6 each R,G,&B.  To do a true gray scale
with a color monitor, you can only define a 64-shade scale.  If
you have a monochrome VGA monitor, there *is* a bios routine to
sum the colors together to make a true gray scale of 256 levels
(I've seen it done, but didn't see the code).

What I've done on my machine is to load the 256 color registers
with each of 0..63 repeated four times to make a semi-smooth
8-bit output.  It works pretty well for dumping 8-bit B&W images
to the monitor.  If anyone needs code, let me know.
-- 
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