Display temperature as a color with C#?
Someone knows an algorithm that gets temperatue in Kelvin/Celsius and returns RGB?
Like in thermal cameras.
I found some links :
http://www.brucelind
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I realize this is a two-year old thread, but I had the same predicament.
I took the data from the color table and did applied piece-wise 5th order polynomial fitting using Numpy.polyfit in Python. From those coefficients I was able to come up with the C# function below. R-squared values for the fits are close to or exceed 0.999. It has less than .01% error through most of its domain, but it does have a couple of points where it is closer to 3%. Should be good enough for most situations though.
private Color blackBodyColor(double temp) { float x = (float)(temp / 1000.0); float x2 = x * x; float x3 = x2 * x; float x4 = x3 * x; float x5 = x4 * x; float R, G, B = 0f; // red if (temp <= 6600) R = 1f; else R = 0.0002889f * x5 - 0.01258f * x4 + 0.2148f * x3 - 1.776f * x2 + 6.907f * x - 8.723f; // green if (temp <= 6600) G = -4.593e-05f * x5 + 0.001424f * x4 - 0.01489f * x3 + 0.0498f * x2 + 0.1669f * x - 0.1653f; else G = -1.308e-07f * x5 + 1.745e-05f * x4 - 0.0009116f * x3 + 0.02348f * x2 - 0.3048f * x + 2.159f; // blue if (temp <= 2000f) B = 0f; else if (temp < 6600f) B = 1.764e-05f * x5 + 0.0003575f * x4 - 0.01554f * x3 + 0.1549f * x2 - 0.3682f * x + 0.2386f; else B = 1f; return Color.FromScRgb(1f, R, G, B); }讨论(0) -
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.
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Color temperature is based on the actual color of light emitted from something (theoretically, an "ideal black body") that emits light based solely on its temperature.
Some examples of this kind of light source: if you have an electric stove element that is glowing red, it might be around 1000K. A regular incandescent bulb filament is around 2700K, and the sun is roughly 5700K. All three are fair approximations of a "black body"; they emit a particular spectrum of light based on their actual temperature.
Many artificial light sources are not actually the "temperature" of the light they emit (and their spectra are generally not black-body spectra, either...). Instead, their "temperature" rating is the temperature a theoretical black body would have to be in order to emit light of that color. There are also colors that cannot be generated by a black body: light which is greenish or purplish compared to a more "natural"-looking black body illumination.
As mentioned in one of the comments, the kind of thermal camera displays you are probably thinking about are all false-color. In a false-color display, the colors are chosen for convenience only: so, for a thermal camera they might choose a "hot"-looking red for warm, and "cold"-looking blue for cold. But, they could just as easily choose a range from black to white, or fuschia to green.
Because false-color displays are arbitrary, you really need to check the color key to a particular image or system if you want to estimate the temperature (scientific images should generally have some kind of color key for this purpose). If you have no color key, and no documentation on how the image was generated, you are out of luck.
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If get you right you are looking for a theoretical background on XYZ color space
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The best option is to use an image with GetPixel:
private void UpdateTemp() { Bitmap temps = (Bitmap)Properties.Resources.temp; if (curTemp >= 0) { int i = curTemp; if (i < 0) i = 0; if (i > temps.Width-1) i = temps.Width-1; this.BackColor = temps.GetPixel(i, 10); } }Or building an array. Source
private static Color[] colors = { Color.FromArgb(155, 188, 255), // 40000 Color.FromArgb(155, 188, 255), // 39500 Color.FromArgb(155, 188, 255), // 39000 Color.FromArgb(155, 188, 255), // 38500 Color.FromArgb(156, 188, 255), // 38000 Color.FromArgb(156, 188, 255), // 37500 Color.FromArgb(156, 189, 255), // 37000 Color.FromArgb(156, 189, 255), // 36500 Color.FromArgb(156, 189, 255), // 36000 Color.FromArgb(157, 189, 255), // 35500 Color.FromArgb(157, 189, 255), // 35000 Color.FromArgb(157, 189, 255), // 34500 Color.FromArgb(157, 189, 255), // 34000 Color.FromArgb(157, 189, 255), // 33500 Color.FromArgb(158, 190, 255), // 33000 Color.FromArgb(158, 190, 255), // 32500 Color.FromArgb(158, 190, 255), // 32000 Color.FromArgb(158, 190, 255), // 31500 Color.FromArgb(159, 190, 255), // 31000 Color.FromArgb(159, 190, 255), // 30500 Color.FromArgb(159, 191, 255), // 30000 Color.FromArgb(159, 191, 255), // 29500 Color.FromArgb(160, 191, 255), // 29000 Color.FromArgb(160, 191, 255), // 28500 Color.FromArgb(160, 191, 255), // 28000 Color.FromArgb(161, 192, 255), // 27500 Color.FromArgb(161, 192, 255), // 27000 Color.FromArgb(161, 192, 255), // 26500 Color.FromArgb(162, 192, 255), // 26000 Color.FromArgb(162, 193, 255), // 25500 Color.FromArgb(163, 193, 255), // 25000 Color.FromArgb(163, 193, 255), // 24500 Color.FromArgb(163, 194, 255), // 24000 Color.FromArgb(164, 194, 255), // 23500 Color.FromArgb(164, 194, 255), // 23000 Color.FromArgb(165, 195, 255), // 22500 Color.FromArgb(166, 195, 255), // 22000 Color.FromArgb(166, 195, 255), // 21500 Color.FromArgb(167, 196, 255), // 21000 Color.FromArgb(168, 196, 255), // 20500 Color.FromArgb(168, 197, 255), // 20000 Color.FromArgb(169, 197, 255), // 19500 Color.FromArgb(170, 198, 255), // 19000 Color.FromArgb(171, 198, 255), // 18500 Color.FromArgb(172, 199, 255), // 18000 Color.FromArgb(173, 200, 255), // 17500 Color.FromArgb(174, 200, 255), // 17000 Color.FromArgb(175, 201, 255), // 16500 Color.FromArgb(176, 202, 255), // 16000 Color.FromArgb(177, 203, 255), // 15500 Color.FromArgb(179, 204, 255), // 15000 Color.FromArgb(180, 205, 255), // 14500 Color.FromArgb(182, 206, 255), // 14000 Color.FromArgb(184, 207, 255), // 13500 Color.FromArgb(186, 208, 255), // 13000 Color.FromArgb(188, 210, 255), // 12500 Color.FromArgb(191, 211, 255), // 12000 Color.FromArgb(193, 213, 255), // 11500 Color.FromArgb(196, 215, 255), // 11000 Color.FromArgb(200, 217, 255), // 10500 Color.FromArgb(204, 219, 255), // 10000 Color.FromArgb(208, 222, 255), // 9500 Color.FromArgb(214, 225, 255), // 9000 Color.FromArgb(220, 229, 255), // 8500 Color.FromArgb(227, 233, 255), // 8000 Color.FromArgb(235, 238, 255), // 7500 Color.FromArgb(245, 243, 255), // 7000 Color.FromArgb(255, 249, 253), // 6500 Color.FromArgb(255, 243, 239), // 6000 Color.FromArgb(255, 236, 224), // 5500 Color.FromArgb(255, 228, 206), // 5000 Color.FromArgb(255, 219, 186), // 4500 Color.FromArgb(255, 209, 163), // 4000 Color.FromArgb(255, 196, 137), // 3500 Color.FromArgb(255, 180, 107), // 3000 Color.FromArgb(255, 161, 72), // 2500 Color.FromArgb(255, 137, 18), // 2000 Color.FromArgb(255, 109, 0), // 1500 Color.FromArgb(255, 51, 0), // 1000 };讨论(0)
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