[argyllcms] Re: Creating Gamut
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 18 May 2012 23:58:04 +1000
Terry Hewitt wrote:
Hi,
> a) Have I mis-understood something?
No.
> b) Do I need to use some switches in iccgamut.exe to ensure this doesn’t
> happen?
No, this is normal. L*a*b* 0,0,0 corresponds to XYZ 0,0,0. It represents
absolute black. Several synthetic profiles (such as sRGB, AdobeRGB etc.)
have a perfect black. Because iccgamut produces 3 Dimensional gamut
surfaces, the black point is a valid surface point of the gamut.
> c) Have I found a bug?
Yes, but in Matlab. x,y values in Yxy become undefined when X+Y+Z is zero.
If you don't want this signalled by a divide by zero error, then you
need to do something to stop that. You could set them to zero, the white
x,y, or something else that makes sense for your particular situation.
Note that x,y is a projection, and since it divides by the sum of X,Y & Z,
the projection "blows up" as you approach X=Y=Z = 0.
Graeme Gill.
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