Patent ID: 7277102

Claim:
A method of rendering an expression tree into a raster pixel image having a plurality of pixel locations, the expression tree having a plurality of nodes comprising one or more binary nodes and a plurality of leaf nodes, wherein each binary node has a left branch to a descendent node and a right branch to another descendent node and represents a binary operation on the two descendent nodes, and wherein each node represents a graphic object having object edges, with one or more of the graphic objects overlapping, the overlapping graphic objects comprising a left node region, a common region, and a right node region, said method comprising the steps of: determining groups of one or more pixel locations, wherein the groups are bounded by the object edges; determining, for each group, whether the left and right branches of the one or more binary nodes are active or inactive; and traversing, for each group, the expression tree, wherein said traversing step comprises the substeps of: checking whether the right and left branches of a previously traversed binary node are active or a left node region is required for the binary operation of the previously traversed binary node and the left branch is active and the right branch is inactive of the previously traversed binary node, and if so, traversing the left branch of the previously traversed binary node to the descendent node; and checking whether the right and left branches of the previously traversed binary node are active or a right node region is required for the binary operation of the previously traversed binary node and the right branch is active and the left branch is inactive of the previously traversed binary node, and if so, traversing the right branch of the previously traversed binary node to the descendent node; generating, for each group, operator instructions for any binary node traversed in said traversing step and having active right and left branches; generating, for each group, leaf value instructions for any leaf node traversed in said traversing step; executing for each group, the generated instructions to render the graphic objects at the one or more pixel locations; and reproducing the rendered graphic objects on a reproduction device.