Scale an image from an absolute point

[Roger.E.Eller at sealedair.com]

I need to scale an image from an absolute point within the image rect. 
This point will not be the loc or any of the 4 corners. The image must 
stay positioned (locked) by a point where the user clicks during the 
scaling routine. Does anyone have an idea of how to best approach this? I 
could calculate the offset from the loc of the image, but this changes as 
the image is dragged to be larger/smaller. Any ideas?

Kind Regards,
Roger Eller <roger.e.eller at sealedair.com>