Distance measure between HSL colours

Question

Hi,

I am coding a program that allows a user to choose various foreground and background colours in RGB. I want to not allow them to chose foreground and backgrounds that are too similar and decided to convert to HSL and use HSL euclidean distance as a way to check for similarity.

Is there a good weighting to use for HSL space (rather than equal weighting for H, S and L)? I've looked at various sites and not found the exact thing I need; just things saying that HSL or HSB is better than RGB.

Answer 1

I don't have exact figures for you, but I'd use a much higher weight for L than H or S. The eye is bad at discriminating between equal colors of different saturation, and nearly as bad at distinguishing different hues - expecially if it's fine detail you're trying to see, like text.

Answer 2

first convert the colors to Lab. This colorspace is designed so that the vectorial difference between any two colors closely approximate a 'subjective distance'.

In color management, a 'delta E' value is given as a measure of how perceptually faithful a given color transformation is. it's just the magnitude of the vector difference between original and final colors as expressed in Lab space.

Answer 3

My advice would be to skip HSL/HSB entirely, and go directly from RGB to LAB. Once you've done that, you can do a standard delta E computation.

Answer 4

Thanks.

I have use Lab and got a Euclidean distance between 2 colours.

Do you have any advice for what a good tolerance is for have text on background - would 50.0 be good?