Display temperature as a color with C#?

Question

Someone knows an algorithm that gets temperatue in Kelvin/Celsius and returns RGB?

Like in thermal cameras.

I found some links :

http://www.brucelind

Answer 1

The above function overestimate red color when temp > 10000 K. Colors turn to purple when temp>14000. I refitted the data with 7th order polynomials. The coefficients of should be:

def temp_to_rgb(temp):
    t = temp/1000.

    # calculate red
    if t < 6.527:
        red = 1.0
    else:
        coeffs = [  4.93596077e+00,  -1.29917429e+00,
                    1.64810386e-01,  -1.16449912e-02,
                    4.86540872e-04,  -1.19453511e-05,
                    1.59255189e-07,  -8.89357601e-10]
        tt = min(t,40)
        red = poly(coeffs,tt)
    red = max(red,0)
    red = min(red,1)

    # calcuate green
    if t < 0.85:
        green = 0.0
    elif t < 6.6:
        coeffs = [ -4.95931720e-01,   1.08442658e+00,
                   -9.17444217e-01,   4.94501179e-01,
                   -1.48487675e-01,   2.49910386e-02,
                   -2.21528530e-03,   8.06118266e-05]
        green = poly(coeffs,t)
    else:
        coeffs = [  3.06119745e+00,  -6.76337896e-01,
                    8.28276286e-02,  -5.72828699e-03,
                    2.35931130e-04,  -5.73391101e-06,
                    7.58711054e-08,  -4.21266737e-10]
        tt = min(t,40)
        green = poly(coeffs,tt)
    green = max(green,0)
    green = min(green,1)

    # calculate blue
    if t < 1.9:
        blue = 0.0
    elif t < 6.6:
        coeffs = [  4.93997706e-01,  -8.59349314e-01,
                    5.45514949e-01,  -1.81694167e-01,
                    4.16704799e-02,  -6.01602324e-03,
                    4.80731598e-04,  -1.61366693e-05]
        blue = poly(coeffs,t)
    else:
        blue = 1.0
    blue = max(blue,0)
    blue = min(blue,1)

    return (red,green,blue)

Here poly(coeffs,x) = coeffs[0] + coeffs[1]*x + coeffs[2]*x**2 + ...

Sorry I am not familiar with C# but you can easily read the codes.

The error is within only 0.5% for most cases and at most 1.2% for red in temp = 6600 K. High order polynomials are adopted here so red and green must keep constant for temp > 40000 K, otherwise strange things will happen.