colour.conversions.rgb2hsl

colour.conversions.rgb2hsl(rgb: Tuple[float, float, float]) → Tuple[float, float, float]

Convert RGB representation towards HSL.

Parameters

  • r – Red amount (float between 0 and 1)

  • g – Green amount (float between 0 and 1)

  • b – Blue amount (float between 0 and 1)

Return type

3-uple for HSL values in float between 0 and 1

This algorithm came from: http://www.easyrgb.com/index.php?X=MATH&H=19#text19

Here are some quick notion of RGB to HSL conversion:

>>> from colour import rgb2hsl

Note that if red amount is equal to green and blue, then you should have a gray value (from black to white).

>>> rgb2hsl((1.0, 1.0, 1.0))  
(..., 0.0, 1.0)
>>> rgb2hsl((0.5, 0.5, 0.5))  
(..., 0.0, 0.5)
>>> rgb2hsl((0.0, 0.0, 0.0))  
(..., 0.0, 0.0)

If only one color is different from the others, it defines the direct Hue:

>>> rgb2hsl((0.5, 0.5, 1.0))  
(0.66..., 1.0, 0.75)
>>> rgb2hsl((0.2, 0.1, 0.1))  
(0.0, 0.33..., 0.15...)

Having only one value set, you can check that:

>>> rgb2hsl((1.0, 0.0, 0.0))
(0.0, 1.0, 0.5)
>>> rgb2hsl((0.0, 1.0, 0.0))  
(0.33..., 1.0, 0.5)
>>> rgb2hsl((0.0, 0.0, 1.0))  
(0.66..., 1.0, 0.5)

Regression check upon very close values in every component of red, green and blue:

>>> rgb2hsl((0.9999999999999999, 1.0, 0.9999999999999994))
(0.0, 0.0, 0.999...)

Of course:

>>> rgb2hsl((0.0, 2.0, 0.5))  
Traceback (most recent call last):
...
ValueError: Green must be between 0 and 1. You provided 2.0.

And: >>> rgb2hsl((0.0, 0.0, 1.5)) # doctest: +ELLIPSIS Traceback (most recent call last): … ValueError: Blue must be between 0 and 1. You provided 1.5.