CODEWITHSUNDEEP
hsl
Lucas Hu
Lucas Hu

Reputation: 159

How to calculate luminance in HSL

Just checked this website http://www.workwithcolor.com/hsl-color-schemer-01.htm and I am curious how to get those numbers in Lum(luminance)? I can not find a proper formula online to get those results. Thanks

Upvotes: 1

Views: 1718

Answers (1)

PillFall
PillFall

Reputation: 164

A way to get the values they show is transforming the colour from sRGB to CIE-XYZ and then from CIE-XYZ to L*a*b* (or CIELAB)

In CIELAB, L* is described as perceptual lightness, that's the value the page shows as Luminance.

You can calculate this value quickly with the following equations, remember that the RGB values must need to be normalized (values from 0 to 1):

Equations

Here is a comparison between this algorithm (L*) and the one in the page (Lum.) using the colours on the color luminance explanation.

Color L* [%] Lum. [%]
#FF0000 53.232881... 54 (53.77)
#FF8000 67.050096... 65 (65.06)
#FFFF00 97.138246... 94 (93.63)
#80FF00 89.910015... 83 (82.96)
#00FF00 87.737033... 80 (79.52)
#00FF80 88.485146... 82 (81.63)
#00FFFF 91.116521... 87 (87.44)
#0080FF 54.718662... 57 (57.36)
#0000FF 32.302586... 44 (43.95)
#8000FF 40.911243... 52 (51.51)
#FF00FF 60.319933... 70 (70.28)
#FF0080 54.884906... 60 (59.59)

Upvotes: 1

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