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# mathebox/color_conversion.py

Created April 12, 2015 16:47
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Python methods to convert colors between RGB, HSV and HSL
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 import math def rgb_to_hsv(r, g, b): r = float(r) g = float(g) b = float(b) high = max(r, g, b) low = min(r, g, b) h, s, v = high, high, high d = high - low s = 0 if high == 0 else d/high if high == low: h = 0.0 else: h = { r: (g - b) / d + (6 if g < b else 0), g: (b - r) / d + 2, b: (r - g) / d + 4, }[high] h /= 6 return h, s, v def hsv_to_rgb(h, s, v): i = math.floor(h*6) f = h*6 - i p = v * (1-s) q = v * (1-f*s) t = v * (1-(1-f)*s) r, g, b = [ (v, t, p), (q, v, p), (p, v, t), (p, q, v), (t, p, v), (v, p, q), ][int(i%6)] return r, g, b def rgb_to_hsl(r, g, b): r = float(r) g = float(g) b = float(b) high = max(r, g, b) low = min(r, g, b) h, s, v = ((high + low) / 2,)*3 if high == low: h = 0.0 s = 0.0 else: d = high - low s = d / (2 - high - low) if l > 0.5 else d / (high + low) h = { r: (g - b) / d + (6 if g < b else 0), g: (b - r) / d + 2, b: (r - g) / d + 4, }[high] h /= 6 return h, s, v def hsl_to_rgb(h, s, l): def hue_to_rgb(p, q, t): t += 1 if t < 0 else 0 t -= 1 if t > 1 else 0 if t < 1/6: return p + (q - p) * 6 * t if t < 1/2: return q if t < 2/3: p + (q - p) * (2/3 - t) * 6 return p if s == 0: r, g, b = l, l, l else: q = l * (1 + s) if l < 0.5 else l + s - l * s p = 2 * l - q r = hue_to_rgb(p, q, h + 1/3) g = hue_to_rgb(p, q, h) b = hue_to_rgb(p, q, h - 1/3) return r, g, b def hsv_to_hsl(h, s, v): l = 0.5 * v * (2 - s) s = v * s / (1 - math.fabs(2*l-1)) return h, s, l def hsl_to_hsv(h, s, l): v = (2*l + s*(1-math.fabs(2*l-1)))/2 s = 2*(v-l)/v return h, s, v

### zangwill commented Oct 13, 2018

@mathebox & @ArtemBernatskyy, According to https://en.wikipedia.org/wiki/HSL_and_HSV, add `l = (high + low) / 2`, and not `low`.

hsl_to_rgb routine is problematic! Please use this!

``````def clamp(value, min_value, max_value):
return max(min_value, min(max_value, value))

def saturate(value):
return clamp(value, 0.0, 1.0)

def hue_to_rgb(h):
r = abs(h * 6.0 - 3.0) - 1.0
g = 2.0 - abs(h * 6.0 - 2.0)
b = 2.0 - abs(h * 6.0 - 4.0)
return saturate(r), saturate(g), saturate(b)

def hsl_to_rgb(h, s, l):
r, g, b = hue_to_rgb(h)
c = (1.0 - abs(2.0 * l - 1.0)) * s
r = (r - 0.5) * c + l
g = (g - 0.5) * c + l
b = (b - 0.5) * c + l
return r, g, b
``````

### nprghu commented Dec 15, 2020

Hi! I have a question, for me `rgb_to_hsv()` is not working. For example, if I put `print(rgb_to_hsv(100,0,0))`, which should print `0, 100, 100`, I got `0, 1, 255`. Something is definitely wrong here.

Hi! I have a question, for me `rgb_to_hsv()` is not working. For example, if I put `print(rgb_to_hsv(100,0,0))`, which should print `0, 100, 100`, I got `0, 1, 255`. Something is definitely wrong here.

The functions takes RGB values in the [0,1] range.

### hugoaboud commented Mar 1, 2021

plz correct `l` to `low` at https://gist.github.com/mathebox/e0805f72e7db3269ec22#file-color_conversion-py-L57

Actually, the fix should be on lines 50 and 65, where the variable names 'h, s, v' are used instead of 'h, s, l'. This complies with @Zangwill's answer.

### alexTitakoff commented Nov 1, 2022

` File "/Users/alexMac/Projects/Freelance/schemochka-local/app/image2schema_lib/stages/schema_builder/cross.py", line 131, in rgb_to_hsl s = d / (2 - high - low) if l > 0.5 else d / (high + low) NameError: name 'l' is not defined`

### alexTitakoff commented Nov 1, 2022

plz correct `l` to `low` at https://gist.github.com/mathebox/e0805f72e7db3269ec22#file-color_conversion-py-L57

Actually, the fix should be on lines 50 and 65, where the variable names 'h, s, v' are used instead of 'h, s, l'. This complies with @Zangwill's answer.

Thanks!