Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!uwmcsd1!marque!lakesys!mikes
From: mikes@lakesys.UUCP (Mike Shawaluk)
Newsgroups: comp.sys.amiga
Subject: Re: grey scale --> HAM picture
Keywords: source, help
Message-ID: <338@lakesys.UUCP>
Date: 1 Feb 89 14:58:19 GMT
References: <6432@thorin.cs.unc.edu> <19763@agate.BERKELEY.EDU>
Reply-To: mikes@lakesys.UUCP (Mike Shawaluk)
Organization: Lake Systems - Milwaukee, Wisconsin
Lines: 34

In article <19763@agate.BERKELEY.EDU> c60a-1fy@web-2a.berkeley.edu (Anon) writes:
>In article <6432@thorin.cs.unc.edu> skinner@unc.cs.unc.edu (Andrew Skinner) writes:
>>
>>I would like to be able to look at the results of work when I am at home.
>>A reasonable approximation would do, so I'd like to be able to convert
>>picture files produced at school to HAM mode pictures, to be displayed
>>by standard programs.  Does anyone have any free source code I could use
>>to convert (8 bit greyscale) images to HAM mode?  I'm sure it would be an
>
>Whatta you want ham for?  There are only 16 shades of grey in the palette 
>anyway, you ham won't gain you anything.  Just use the 4 msb's and convert
>to a 4-plane hires picture.

This reply to Andrew's original message, and a few others, have pointed out
that HAM won't buy anything in regard to viewing grey-scale images, since
there are only 16 possible shades of grey that can be generated using the
Amiga's 4096 color pallette.  However, Andrew didn't say (at least I didn't
SEE him say it; I don't have the original article, only replies to his
posting) what the resolution of the 8-bit grey scale images was.  If they are
less that 640 by 400, then additional grey shade can be generated by
dithering.  I won't go into a technical discussion of it here, because I'm
not that well-versed on the technical details, but only on the fact that it
should work, provided that the images being imported are of a lower pixel
resolution that 640 x 400.  I should mention that you probably wouldn't be
able to get 256 levels of grey by dithering, even if you went to 320 by 200
effective resolution, and that you'd probably get some flicker because of the
interlace, although if the images are smoothly shaded, the flicker should be
pretty minimal.  Would someone with the appropriate technical background on
graphics and dithering please fill in the gaps in what I've said above (i.e,
tell me if I'm full of $#!+ or not...)

-- 
   - Mike Shawaluk
     ...!uunet!marque!lakesys!mikes