HSL/HSV/HSI Blog

Cylindrical Coordinate System:-Cylindrical co-ordinate system is a three dimensional co-ordinate system that specifies point positions by the distance from a chosen reference axis,the direction from the axis relative to a chosen reference direction & the distance from a chosen reference plane perpendicular to the axis.The latter distance is given as a positive or negative no depending on which side of reference plane faces the point.
        HSL & HSV are the two most common cylindrical co-ordinate system.HSL & HSV are developed  in 1970.They are widely used today in color pickers in image editing software,less commonly in image analysis
& computer vision.

HSV:-HSV stands for Hue,saturation & value.often also called HSB ,B for brightness. It is also called hex cone model.
HSL:- HSL stands for hue,saturation & light ,often also callled HLS.It is also called double hex cone model.

*We can calculate Chroma from RGB with the following formula :-



*We can calculate Hue from RGB with the following formula :-



*We can calculate Lightness from following formula :-

(i)In the HSI model intensity is defined as average of three components:

           I = 1/3(R+G+B)

(ii)In the HSV "hexcone" model value is defined as the largest component of color.

          V=M=max(R,G,B)
(iii)In the bi-hexcone model lightness is defined as the average of largest & smallest color component.

          L= 1/2(M+m)

(iv)Luma is the weighted average of gamma corrected R,G & B

        

* Following are the formula for the saturation for HSV,HSL & HSI:-

 




Uses of HSI,HSV & HSL:-HSI ,HSV & HSL are often used computer vision,Image analysis for feature detection & image segmentation.It is used in robot vision ,object recognition,content based image analysis & analysis of medical images.It is also used in color pickers of image editors.


HSL to RGB:-
 For converting HSL to RGB ,First of all ,we need to compute chroma:-

                                  

                                            where C is Chroma
                                            L for Lightness
                                            Shsl for saturation


Next,we find the point on one of the bottom three faces of the RGB cube which has the same hue & chroma as our color.

       




Finally ,we add the equal amounts of R,G & B to reach the proper value.

HSV to RGB:-

 For converting HSV to RGB ,First of all ,we need to compute chroma,by multiplying saturation by the maximum chroma for a given value.


                                             
                                            where C is Chroma
                                            V for value
                                            Shsv for saturation


Next,we find the point on one of the bottom three faces of the RGB cube which has the same hue & chroma as our color.

       




Finally ,we add the equal amounts of R,G & B to reach the proper value.



Luma/Chroma/Hue to RGB:-

Here we already have Hue & Chroma so we use same strategy:-

 




Finally ,we add the equal amounts of R,G & B to reach the proper value.