diff nonExposed/utils/rgb2hsl.m @ 14:b1901e8d8f5f

initial commit

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nonExposed/utils/rgb2hsl.m	Tue Mar 17 09:34:13 2015 +0100
@@ -0,0 +1,54 @@
+function hsl=rgb2hsl(rgb)
+
+%Converts Red-Green-Blue Color value to Hue-Saturation-Luminance Color value
+%
+%Usage
+%       HSL = rgb2hsl(RGB)
+%
+%   converts RGB, a M X 3 color matrix with values between 0 and 1
+%   into HSL, a M X 3 color matrix with values between 0 and 1
+%
+%See also hsl2rgb, rgb2hsv, hsv2rgb
+
+%Suresh E Joel, April 26,2003
+
+if nargin<1,
+    error('Too few arguements for rgb2hsl');
+    return;
+elseif nargin>1,
+    error('Too many arguements for rgb2hsl');
+    return;
+end;
+
+if max(max(rgb))>1 | min(min(rgb))<0,
+    error('RGB values have to be between 0 and 1');
+    return;
+end;
+
+for i=1:size(rgb,1),
+    mx=max(rgb(i,:));%max of the 3 colors
+    mn=min(rgb(i,:));%min of the 3 colors
+    imx=find(rgb(i,:)==mx);%which color has the max
+    hsl(i,3)=(mx+mn)/2;%luminance is half of max value + min value
+    if(mx-mn)==0,%if all three colors have same value, 
+        hsl(i,2)=0;%then s=0 and 
+        hsl(i,1)=0;%h is undefined but for practical reasons 0
+        return;
+    end;
+    if hsl(i,3)<0.5,
+        hsl(i,2)=(mx-mn)/(mx+mn);
+    else
+        hsl(i,2)=(mx-mn)/(2-(mx+mn));
+    end;
+    switch(imx(1))%if two colors have same value and be the maximum, use the first color
+    case 1 %Red is the max color
+        hsl(i,1)=((rgb(i,2)-rgb(i,3))/(mx-mn))/6;
+    case 2 %Green is the max color
+        hsl(i,1)=(2+(rgb(i,3)-rgb(i,1))/(mx-mn))/6;
+    case 3 %Blue is the max color
+        hsl(i,1)=(4+(rgb(i,1)-rgb(i,2))/(mx-mn))/6;
+    end;
+    if hsl(i,1)<0,hsl(i,1)=hsl(i,1)+1;end;%if hue is negative, add 1 to get it within 0 and 1
+end;
+
+hsl=round(hsl*100000)/100000; %Sometimes the result is 1+eps instead of 1 or 0-eps instead of 0 ... so to get rid of this I am rounding to 5 decimal places)
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