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From: stroyan@hpfcso.FC.HP.COM (Mike Stroyan)
Newsgroups: comp.sys.hp
Subject: Re: Snake Color Graphics
Message-ID: <7370387@hpfcso.FC.HP.COM>
Date: 4 May 91 23:50:39 GMT
References: <1991May1.125642.8406@usenet.ins.cwru.edu>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 19

> 	Can someone tell me what the pixel format for the GRX or CRX
> frame buffers is. (i.e. what is the 8 bit pixel format for pseudocolo,
> is it 8 bit out to an 8,8,8 pseudo RAMDAC or is it organnized as 3,3,2
> or ?????)
> Pedro J. Diaz, Ph.D.	| CWRU School of Engineering/School of Medicine	

The CRX display has 8 bits per pixel.  Each pixel index is mapped
through color map to red, green, and blue intensity.  There are 8 bits
for each of red, green, and blue.  The GRX display just maps each index
to one grey intensity.

One wrinkle on this is that there are actually 16 frame buffer planes
arranged into two 8 plane banks to allow double buffering.  There is
another plane which selects which bank is displayed on a pixel by pixel
basis.  This allows independent double buffering of multiple windows in
X.  The bank select feature is not supported directly by the X server.
It is only accessible through the Starbase or PHIGS graphics libraries.

Mike Stroyan, mike_stroyan@fc.hp.com