SIOX

[Michael Thaler]

Hello,

I just wanted to ask if anybody is working on porting the siox foreground 
selection tool from gimp to krita. If not, I might give it a try.

I had a brief look at gimp's siox foreground selection tool. Internally it 
uses a LAB colorspace. It is defined in the following way:

typedef struct
{
	gfloat l;
	gfloat a;
	gloat b;
	gint cardinality;
} lab;

I was pleased to see that Krita already has functions to convert to and from 
LAB. But Krita uses:

fromLab(float l, float a, float b, float alpha, KisProfileSP profile = 0);

So, l, a, b are identical, but the siox tool uses gint cardinality while krita 
uses float alpha. How are they related?

I had a look at http://en.wikipedia.org/wiki/Lab_color_space, but they write 
nothing about the fourth component. Is there a online article that actually 
describes lab in more detail?

Greetings,
Michael