Abstract: A computer system for production of ink separations from an object-based print pre-process apparatus using a page description language. The print pre-process system facilitates creation of object spreads for any combination or configuration of objects on the rendered page. For each object on a rendered page, the computer system 100 makes use of a spread table to determine spread incidences. For each spread incidence, the computer system generates set union, intersection, difference, and edge extraction for spreading, receiving, and obstructing objects to create a simplified graph of contour histories providing a visible portion of the spread object. The visible boundary between the visible spread object and the receiving object is then extracted. The visible boundary is strokeable within a clipped window set to the receiving object. The stroke color and width, set by the spread table, can be knockout print or overprint.