I can't understand the difference between HSL and HSI. Are they the same? Do you use the same algorithm to convert RGB -> HSL and RGB -> HSI?
36.3k 27 27 gold badges 137 137 silver badges 194 194 bronze badges asked Jun 27, 2012 at 21:08 user1486293 user1486293 79 1 1 gold badge 2 2 silver badges 5 5 bronze badges The Wikipedia article should explain everything you need to know. Commented Jun 27, 2012 at 21:09 If I understood that I would not have asked. Commented Jun 27, 2012 at 21:10 Commented Jun 27, 2012 at 21:14@user1486293: The article explains the difference between HSL, HSV and HSI, and gives conversion formulae.
Commented Jun 27, 2012 at 21:22@OliCharlesworth, that is the most complete reference I've ever seen on the subject. Thanks for the link.
Commented Jun 27, 2012 at 21:41Here's a comparison between HSV / HSL / HSI color spaces. I think it's important to keep in mind that these models come from a projection of the RGB cube. For more details on this, check the Wikipedia page (specially this figure) and this answer on Stack Overflow.
Their hues are approximately the same. For HSI [1]:
in which v_x and v_y are the coordinates from the resulting RGB vector and R , G and B were already normalised to the range [0,1] (i.e. divide the values from the range [0,255] by 255). If v_y
For HSL and HSV, we first calculate the (normalised) chroma: C = M - m = max(R,G,B) - min(R,G,B) (again, with RGB already normalised to the range [0,1]). Then we use the piece-wise formulation:
Finally, H = H' * 60° . If C = 0 , we may declare H = 0° .
The expressions for saturation and value/lightness/intensity are shown below:
Saturation and V/L/I figures source: Wikipedia
[1] Rafael C. Gonzalez, Richard E. Woods. Digital Image Processing, 4ed. New York, NY: Pearson. 2018. ISBN-13: 9780133356724. sec. 7.2: Color Models.
