History of 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.