NSImage -setSize problem

[Enrico Sersale]

I'm using, in GDraw, an image as a template on which you can draw. (as
in Illustrator, if somebody knows it).
The problem is that, when I zoom on a point, also this background image
should change its size according with the new zoom factor.
Well, I've tryied NSImage -setSize, NSImageRep -setSize and -drawInRect
but without success...
Can I, actually, scale an image?
And, if I can, wath do I have to do?