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

%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;
}

See Also

lab2rgb

Comments

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