Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!ucbvax!gergle.UUCP!greg
From: greg@gergle.UUCP
Newsgroups: comp.windows.news
Subject: Re:  Scaling bitmapped images - help wanted
Message-ID: <8805120554.AA01942@parallax.parallax.com>
Date: 12 May 88 07:09:08 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 22


	>I have worked out some algorithms for doing the scaling, but they
	>are either too slow, or not able to handle scaling by fractional
	>amounts.  I have not been able to find any literature on the
	>subject, either in the Sun manuals, or elsewhere.  I am sure there
	>must be something, because in PostScript you can just say
	>"x y scale". 

The quick and dirty way is to skip pixels or use pixels more than once 
while building a destination image from the source image. This works 
for any ratio of sizes.

An error variable is kept based on the ratio of the src & dst sizes.

This technique works well in software and in hardware. By well I mean 
my personal judgement of the speed of the operation versus the quality
of the resulting image.  The Sun NeWS port uses this technique in software,
and the Parallax NeWS port has this function in hardware and in software.

The only type of image it will look terrible on are CAD images.

	-greg.