RE: [Algorithms] 256 colour palette

[Stephen J B. <sj...@li...>]

On Wed, 30 Aug 2000, Tom Nettleship wrote:

> > From: Akbar A. [mailto:sye...@ea...]
> > 
> > >since the human eye see R & G better than Blue.
> > more at green
> 
> True. But, as I stated earlier, this can be a bad thing (tm) as
> you don't get a pure grey ramp... just lots of icky slightly
> off greys in your palette, so its worth avoiding.

Suppose you have one extra bit of Green - compared to
Red and Blue....you just have to set up the colour
lookup table such that even numbered green inputs
have the same output as the corresponding R and B
entries.

Hence, R=8, G=16, B=8 would be an exact grey, but
       R=8, G=15, B=8 would be a purplish grey and
       R=8, G=17, B=8 would be a greenish grey.

Then, so long as your greys have identical numbers for
Red and Blue and even numbered Greens, you'll get perfect
greys with the in between green values used for non-grey-scale
colours.

The (slight) lossage here is that you can't quite get
maximum brightness Red or Blue entries.

Steve Baker                      (817)619-2657 (Vox/Vox-Mail)
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