Predefined Functions – lum

Function name: lum – Return luminance of argument
Synopsis: lum(c)

Input data type Output data type
color real


This function takes a color variable as input and returns the luminance of the color. The luminance of a color is always between 0 and 1. For more information about hue, saturation and luminance see HSL Colorspace.

Colors can be created by using one of the color creation functions:

Internally colors are stored in RGBA format. So in order to return the luminance of a color, this function needs to do a color space conversion, which is quite slow.