Patent ID: 7538770

Claim:
A method of rendering a graphical image described by an expression tree in scan line raster order, said expression tree comprising one or more parent nodes and one or more leaf nodes, each said parent node representing a graphical operator and each said leaf node representing a graphic object, said method comprising the steps of: (a) for each scan line, detecting one or more leaf nodes which intersect with a current scan line, updating an activity state of said leaf nodes stored in an operand table, and determining spans of one or more pixel locations each said span being contributed to by a unique combination of one or more said graphical objects; (b) determining, for each said span, the activity state in the updated operand table and a predefined function for each corresponding said operator; (c) generating for each active one of said operators, optimized compositing instructions and pixel generation instructions for a plurality of graphic objects that contribute to said span, said optimized compositing instructions being stored in an operator queue; (d) concurrently generating pixel colors for the plurality of graphic objects that contribute to said span, said pixel colors being buffered in an operand queue; and (e) compositing the generated pixel colors from the operand queue, for each pixel in said span, using the operators defined in the operator queue to output a composited pixel value for each pixel in said span, wherein said steps (a), (b), (c), (d) and (e) are performed by a computer processor.