Creating a Colour Wheel in lab colour space

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Justin
Justin on 25 Apr 2012
Hello Matlab community, I don't seem to be having much luck figuring this out on my own, so I thought I would appeal to you folks on here. I'm very new to MATLAB and so please forgive my rather simplistic questions here.
But what I need to do for an experiment is to generate a colour wheel that would look something like this: http://colors.napcsweb.com/colorschemer/images/cs_RYB.gif
But the wheel itself needs to be in CIELAB colour space. I don't really understand how to start doing this. We ran a previous experiment in my lab that contained a colour wheel in the HSV space . . .I've included the first part of the code below where it generates 252 colours in HSV space. Basically I need to do something like this, but generated in the CIELAB space. Any thoughts/ideas?
Thanks so much in advance.
for i = 1:252
val = 1/252*i
H = val;
S = 1;
V = 1;
if S == 0 %HSV from 0 to 1
R = V * 255;
G = V * 255;
B = V * 255;
else
var_h = H * 6;
if ( var_h == 6 )
var_h = 0; %//H must be < 1
end
var_i = floor( var_h ); %//Or ... var_i = floor( var_h );
var_1 = V * ( 1 - S );
var_2 = V * ( 1 - S * ( var_h - var_i ) );
var_3 = V * ( 1 - S * ( 1 - ( var_h - var_i ) ) );
if ( ar_i == 0 )
var_r = V ;
var_g = var_3 ;
var_b = var_1 ;
elseif ( var_i == 1 )
var_r = var_2 ;
var_g = V ;
var_b = var_1 ;
elseif ( var_i == 2 )
var_r = var_1 ;
var_g = V ;
var_b = var_3 ;
elseif ( var_i == 3 )
var_r = var_1 ;
var_g = var_2 ;
var_b = V ;
elseif ( var_i == 4 )
var_r = var_3 ;
var_g = var_1 ;
var_b = V ;
else
var_r = V ;
var_g = var_1 ;
var_b = var_2 ;
end
R = var_r * 255 ; % //RGB results from 0 to 255
G = var_g * 255;
B = var_b * 255;
end
newmap(i,1:3) = [R G B];
  1 Comment
irvin rynning
irvin rynning on 27 May 2013
Edited: irvin rynning on 27 May 2013
Did you ever get it to work? your link to the colours is broken by the way, and you are missing an end which terminates the for loop

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Answers (2)

Daniel Shub
Daniel Shub on 25 Apr 2012
I believe you can convert your RGB values to CIELAB with colorspace from the FEX.

Image Analyst
Image Analyst on 27 May 2013
You might be able to find it here: http://www.mathworks.com/matlabcentral/fileexchange/40640-computational-colour-science-using-matlab-2e in Stephen Westland's File Exchange. He's the professor who quite literally wrote the book on colour science using MATLAB.

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