Vector map planarization and trapping

Abstract

A vector map representation of page information to perform trapping. The vector map representation combines the positive attributes of both raster and vector based representations to make trapping more efficient by combining the sparseness of the vector representation and the constant unit complexity of the raster representation. In the preferred embodiment of the invention, a page is defined by tiles, and each tile is mapped to a 2-D array of edge pointers referred to as the vector map. Each cell in the vector map contains a list of all of the edges of the image that pass through it. A pair of edges can only interact if they are in the same vector map cell list. Thus, edge intersection and color finding tests are localized as with raster based trapping while the data sparseness of vector based trapping is retained. For a suitably chosen vector map size, a single edge generally does not intersect many cells. A trapping function is applied to edges as determined from the vector map.