Auto Centering
It is standard practice to auto-center the data on the mask. This means that the
program must compute the number of cells that can be placed in X and Y and
based on that number, the cell’s dimensions and the street value, add an offset to the lower left cell
placement to insure that the effective margin is equal all the way around.
if first cell is placed at margin, the array does not center on the mask.
the offset is computed in order to center the array on the mask.
