Question

I’m looking for a colormap library which converts a given value into red, green and blue values. Similar to the colormap feature of matlab [1]. Preferrably in C++.

[1] http://www.mathworks.com/help/techdoc/ref/colormap.html

Answer 1

In think this is way too simple for a library personally i’ve implemented it my self their is the example in C++ (you can look up wikipedia for the math explanation):

/* 
* Computes the color gradiant
* color: the output vector 
* x: the gradiant (beetween 0 and 360)
* min and max: variation of the RGB channels (Move3D 0 -> 1)
*/

void GroundColorMix(double* color, double x, double min, double max)
{
   /*
    * Red = 0
    * Green = 1
    * Blue = 2
    */
    double posSlope = (max-min)/60;
    double negSlope = (min-max)/60;

    if( x < 60 )
    {
        color[0] = max;
        color[1] = posSlope*x+min;
        color[2] = min;
        return;
    }
    else if ( x < 120 )
    {
        color[0] = negSlope*x+2*max+min;
        color[1] = max;
        color[2] = min;
        return;
    }
    else if ( x < 180  )
    {
        color[0] = min;
        color[1] = max;
        color[2] = posSlope*x-2*max+min;
        return;
    }
    else if ( x < 240  )
    {
        color[0] = min;
        color[1] = negSlope*x+4*max+min;
        color[2] = max;
        return;
    }
    else if ( x < 300  )
    {
        color[0] = posSlope*x-4*max+min;
        color[1] = min;
        color[2] = max;
        return;
    }
    else
    {
        color[0] = max;
        color[1] = min;
        color[2] = negSlope*x+6*max;
        return;
    }
}