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From: curtj@pogo.TEK.COM (Curt Jutzi)
Newsgroups: comp.graphics
Subject: Re: N-bit greyscale to n-bit greyscale
Message-ID: <3318@pogo.TEK.COM>
Date: Fri, 24-Apr-87 11:07:46 EST
Article-I.D.: pogo.3318
Posted: Fri Apr 24 11:07:46 1987
Date-Received: Sun, 26-Apr-87 00:48:48 EST
References: <4231@nsc.nsc.com>
Reply-To: curtj@pogo.UUCP (Curt Jutzi)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 25

In article <4231@nsc.nsc.com> misha@nsc.nsc.com (Michael Umansky) writes:
>Hello.
>Example:
>	I have a bitmap image with 8 bits per pixel.
>	Now, I have a monochrome TTL monitor which requires 1 bit per pixel.
>	I need to convert the 8-bit-pixel image to 1-bit-pixel image and
>	still be able to distinguish original shapes and lines.
>

	The way I have always seen it done is by taking the (RGB) values
	and converting them to (YIQ).  From this format you take the 
	intensity (I believe that it is "I" component) which should go
	from 0..255, and use a dithering scheme to approximate the 
	half-tone.

	The rgb->yiq conversion as well as a simple dithering scheme
	are both FOLY & VAN DAM

_______________________________________________________________________________

Curt Jutzi			tektronix!pogo!curtj
c/o tektronix			(503) 685-3723
del. st. 63-356
P.O. Box 1000
Wilsonville, OR 97070