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From: forsythe@convex.com (Charles Forsythe)
Newsgroups: comp.graphics
Subject: Re: need 1x1 blur
Message-ID: <5249@convex.convex.com>
Date: 7 Feb 90 21:01:14 GMT
References: <751@npiatl.UUCP>
Sender: news@convex.com
Distribution: usa
Lines: 30

dkelly@npiatl.UUCP (Dwight Kelly) writes:
>I am looking for a nxn blur function that would remove edges and sharp
>transitions from a color image.  The blur would make a hires RGB image
>suitable for NTSC display.  Would a low-pass filter transfer function work?

Basically...

>Any ideas?

Here's some things that come to my mind:

	-  Keep in mind that an NTSC is quantized vertically and analog
	   horzontally.  Although from a signal processing standpoint,
	   this can be ignored (sort of), there is an important effect
	   from interlace:  horizontal lines one scan-line high flash
	   annoyingly.  You may want to compensate by actually reducing
	   vertical bandwidth a little less than the available maximum.

	-  NTSC Color information is 1/2 the badwidth of black and white. You
	   might want to covert to YIQ coordinates and filter the IQ to
	   more than the Y.  Filtering the Y to match the IQ, which you
	   would end up doing if you just filter RGB, will rob you of
	   available detail.

-Charles
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