Re: Summary: Image negative to positive algorithms

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Article #719

#719

From: Tripp Lilley
Date: Tue, 08 Sep 1992 19:29

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> The colour version seems to lose contrast and have an unwanted tinge. 
> We are currently trying to overcome this.

   The RGB values are not weighted equally.  Silly me, i can't remember
which has more weight, but it's something on the order of .3*R + .3*B +
.4*G == 1  (do not assume that those are the correct weights... someone
out there should know them and post them since i am in the midst of a brain
fart.)   so... in order to create a negative from a positive, 

  Xn is COLOR_X(new version)  Xo is COLOR_X(old version)

  Rn = .3*(Rmax - Ro)
  Bn = .3*(Bmax - Bo)
  Gn = .4*(Gmax - Go)
  Here again, Rn + Bn + Gn should add up to 1... now you multiply these
values by whatever your maxShade is (64 for VGA? 256?)

ii may have gotten the math horribly wrong on this. if so, take what's in the 
first paragraph, and figger it out from there <grin>

 -t.
-- 
-------------------------------------------------------------------------------
|  Tripp Lilley   -- APDENT@actor.realtime.cs.vt.edu                          |
| Nuisance to all, benefit to fewer...but often found being cheerfully paisley|
| >>>  my opinions are.                                                       |

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Path: arc1-ca.pugleaf.net!sparky!uunet!vtserf!creatures!actor.realtime.cs.vt.edu!apdent
From: apdent@actor.realtime.cs.vt.edu (Tripp Lilley)
Newsgroups: comp.fonts
Subject: Re: Summary: Image negative to positive algorithms
Message-ID: <3431@creatures.cs.vt.edu>
Date: 8 Sep 92 19:29:15 GMT
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Organization: Actor Project @ Virginia Tech
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