Reversal is intended to reverse the polarity of a layout by subtracting the set of polygons from a rectangular frame. This function is quite useful for preparing reticles for pattern generators.
The Frame Window
The dimensions of the window can be automatically computed by determining the extents of the polygons to be reveresed. However in most cases, the user will want to either specify his own window or will want to specify a margin to be added to the extents.
LLx=65, LLy=920, URx=320, URy=600.
After Image Reversal. Note that cut-lines are needed to form the voids. There is also an option to use butting polygons to avoid cut-lines.