CODEWITHSUNDEEP
image-processingcolorscomputer-vision
user1486293
user1486293

Reputation: 79

HSL vs HSI color spaces

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?

Upvotes: 3

Views: 4183

Answers (2)

Star Brilliant
Star Brilliant

Reputation: 3126

Here'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.

Hue

Their hues are approximately the same. For HSI [1]:

formula_hue_HSI

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<0, the correction H = 360° - θ is needed (otherwise, H = θ). You may also find different formulae/algorithms depending on the text, but wielding same results.

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:

formula_hue_HSL_HSV

Finally, H = H' * 60°. If C = 0, we may declare H = 0°.

Saturation and Value/Lightness/Intensity

The expressions for saturation and value/lightness/intensity are shown below:

HSV vs HSL HSI

Sources and References

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.

Upvotes: 4

andrew cooke
andrew cooke

Reputation: 46882

They are not the same. You cannot use the same functions to convert from RGB.

Upvotes: -1

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