%
% calculate the white cross-hair as always center of the current image
% evaluate the virtual center coords for it's mark
%
% for the other colors, evaluate the virtual distance from virtual center as where
% they are drawn
%
% if the V checkbox is on, the coords of the crosshair change with all new mark moves
% effectively locking it into the image
%
% each croshair has it's own x/y, relative to the white. If the V checkbox is on
% those coordinates change along with the physical coordinates
%