CssCrush\Color::rgbToHsl
http://mjijackson.com/2008/02/ rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
Converts an RGB color value to HSL. Conversion formula adapted from http://en.wikipedia.org/wiki/HSL_color_space. Assumes r, g, and b are contained in the set [0, 255] and returns h, s, and l in the set [0, 1].
Signature
public function rgbToHsl(array
$rgba )
Parameters
$rgba
— array