Re: [Algorithms] 256 colour palette

[Gil G. <gg...@ma...>]

This isn't right steve. RGB(8,16,8) = (8/31,16/63,8/31) in 565. Oddly, the
divisor is not a power of two, because 31, not 32 is the maximum value that
can be stored in 5 bits.
-Gil

> > 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)
> L3Com/Link Simulation & Training (817)619-2466 (Fax)
> Work: sj...@li...           http://www.link.com
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>
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