Re: [Matplotlib-users] obscure colormapping issue related to quantization

[Perry G. <pe...@st...>]

On Aug 2, 2005, at 5:30 PM, Danny Shevitz wrote:
> But... your last idea is superb. Why not a different way of doing it? 
> How about instead of a lookup table, I just
> write a colormap that has three user defined functions. Then I could 
> do the thresholding exactly. It seems like
> it would be pretty easy to do. I had originally thought colormaps were 
> needed because graphics drivers had finite resolutions
> so you couldn't put up too many colors. So, if I were to create a 
> "functionColormap" instead of a "linearSegmentedColormap"
> with millions of points in the image is there a danger I would run out 
> of colors or is there some internal rounding or truncation
> to prevent this? If there is no problem, then a new colormap subclass 
> is definately the way to go. I assume it would be slower, but
> I'm not sure it matters.
>
> D
>
Yes, I'm thinking some sort of functional, rather than table lookup, 
version would be useful. The table lookup is fast, but has its 
limitations for this kind of problem. I'll think a bit about it too. 
This kind of request comes up regularly (in one form or another) that 
it deserves some sort of solution.

Perry