| US 7,538,770 B2 | ||
| Tree-based compositing system | ||
| Yu-Ling Chen, Epping (Australia) | ||
| Assigned to Canon Kabushiki Kaisha, Tokyo (Japan) | ||
| Filed on Nov. 24, 2004, as Appl. No. 10/995,302. | ||
| Claims priority of application No. 2003906614 (AU), filed on Nov. 28, 2003. | ||
| Prior Publication US 2005/0122337 A1, Jun. 09, 2005 | ||
| Int. Cl. G06T 15/00 (2006.01) | ||
| U.S. Cl. 345—440 [345/421; 345/598; 345/629; 382/240; 700/11; 700/21; 707/102] | 32 Claims |
| 1. 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.
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