Re: Explicit color for pm3d

[Ethan A M. <sf...@us...>]

On Friday, March 25, 2011 10:15:28 am Douglas Mason wrote:
> Dear Developers,
> 
> There's a little discussion going on at the bug request tracker about making
> an explicit color column for pm3d. The idea is that rgbimage and "w p lc
> var" allow you to color each point with an explicit color, not interpolating
> on a palette. Since pm3d offers options like "corner2colors", which tells
> pm3d to use a color that is NOT interpolated among nearby points, it seems
> reasonable that a pm3d option could be made for explicit colors.
> 
> I was wondering what to make of this related paragraph in the documentation:
> 
> "Another drawing algorithm, which would draw quadrangles around a given node
> by taking corners from averaged (x,y)-coordinates of its surrounding 4 nodes
> while using node�s color, could be implemented in the future. This is
> already done for drawing images (2D grids) via image and rgbimage styles."
> 
> I'd love to hear people's thoughts on the possibility of implementing such a
> feature. If not, can anyone suggest another program that does this?

I think that particular hypothetical feature is not what you want.
It would guarantee that every color value is the result of interpolation,
which generally works badly for RGB colors.

Instead, as summarized on the tracker, I think you want an additional option
to pm3d that specifies a mapping function Gray_value -> RGB_Color, where
Gray_value is not a true continuous value running from [0:1] but instead
runs from [0 : 2^24] so that  int(Gray_value) is a 24-bit RGB color spec.

Although I am not so familiar with the code for pm3d, this sounds possible.
Am I failing to see some fundamental difficulty?