Python methods to convert colors between RGB, HSV and HSL

color_conversion.py

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

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

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.

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.

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

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!