Editing rgb2lab - FilterMeisterWiki

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= rgb2lab =

== Syntax ==
{{int rgb2lab(int r, int g, int b, int z)}}

== Arguments ==
:'''r'''
::Red value
:'''g'''
::Green value
:'''b'''
::Blue value
:'''z'''
::Determines which value is returned. z=0 for L, z=1 for a, z=2 for b

== Return ==
Returns the L, a or b value from 0 to 255 depending on the value of z

== Description ==
Lets you convert RGB values to Lab values.

== Example ==
<code>
%ffp

ctl(0):"L Adjust",Range=(-255,255),val=0
ctl(1):"a Adjust",Range=(-255,255),val=0
ctl(2):"b Adjust",Range=(-255,255),val=0

ForEveryTile:{
		
  int r,g,b,l,a,b2;

for (y= y_start; y < y_end; y++) {

if (updateProgress(y, y_end)) abort();

for (x = x_start; x < x_end; x++) {
				
      r = src(x,y,0);
      g = src(x,y,1);
      b = src(x,y,2);

l = rgb2lab (r,g,b,0);
      a = rgb2lab (r,g,b,1); 
      b2 = rgb2lab (r,g,b,2);

// Do the Lab adjustment
      l = l + ctl(0);
      a = a + ctl(1);
      b2 = b2 + ctl(2);

r = lab2rgb (l,a,b2,0);
      g = lab2rgb (l,a,b2,1);
      b = lab2rgb (l,a,b2,2);

pset( x, y, 0, r );
      pset( x, y, 1, g );
      pset( x, y, 2, b );

}
  }

return true;
}
</code>

== See Also ==
((lab2rgb))

== Comments ==
Everyone can add his comments about his experiences with this function here. Tips for using it are welcome, too.

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