topic Re: ArcGIS python HSV to RGB colour conversion in Geoprocessing Questions

ArcGIS python HSV to RGB colour conversion

JohnMcGlynn — Tue, 13 Feb 2024 03:06:48 GMT

I am trying to populate 3 fields in a feature class with the symbology colour in RGB.
My conversion code takes the H, S and V values given by the layer.symbology.renderer.symbol.color function.

A sample of the output from the color function is: {'HSV': [61, 50, 55, 100]}

The values must be munged to cater for the ArcGIS colour model ;

My code is:

def colourHSVtoRGB(self,H,S,V): # The ArcGIS HSV model is strange - Hue 0-240, Saturation 0 - 255, Value 0 - 255 from matplotlib.colors import hsv_to_rgb # Convert hval to 360 and make it 0 - 1 hval = 3.6 * (H / 240) sval = S / 255 vval = V / 255 invals = [hval, sval, vval] rg = hsv_to_rgb(invals) R = rg[0] G = rg[1] B = rg[2] # Convert to 0 - 255 R = int(round((R * 255), 0)) G = int(round((G * 255), 0)) B = int(round((B * 255), 0))

Unfortunately this gives the incorrect RGB values.

From a colour web site, the RGB for HSV = 61, 50, 55 should be 139, 140, 70, which also looks like the correct colour.

My function outputs RGB values; 49, 55, 44 - clearly wrong.
The input values to the matplotlib function are all 0 - 1. I'm sure my interpretation of the calculation for this input could use some improvement.

Thanks,

Re: ArcGIS python HSV to RGB colour conversion

JohnMcGlynn — Wed, 14 Feb 2024 01:18:49 GMT

I was able to fix this by using the algorithm at rapidtables.

Unlike the data given in the ESRI documentation (hue = 0 - 240, saturation = 0 - 255, value = 0 - 255) the actual HSV format is hue 0 - 360, saturation 0 - 100, value 0 - 100

The code is now:

def colourHSVtoRGB(self,H,S,V): # The ArcGIS HSV model is - Hue 0-360, Saturation Pct, Value Pct # Algorithm from https://www.rapidtables.com/convert/color/hsv-to-rgb.html hval = H if hval == 360: hval = 0 sval = S / 100 vval = V / 100 C = sval * vval tr = abs((hval / 60 % 2) - 1) X = C * (1 - tr) if 0 <= H and H < 60: R = C G = X B = 0 elif 60 <= H and H < 120: R = X G = C B = 0 elif 120 <= H and H < 180: R = 0 G = C B = X elif 180 <= H and H < 240: R = 0 G = X B = C elif 240 <= H and H < 300: R = X G = 0 B = C elif 300 <= H and H < 360: R = C G = 0 B = X m = vval - C R = int(round(255 * (R + m),0)) G = int(round(255 * (G + m),0)) B = int(round(255 * (B + m),0)) return R, G, B

John

Re: ArcGIS python HSV to RGB colour conversion

Jeff-Reinhart — Fri, 08 May 2026 20:32:01 GMT

Nice work! Thank you! You just saved me a mess of boring clicks. 🎉