Rasterizing stacked graphics objects from top to bottom

Abstract

Methods and apparatus, including computer program products, for rasterizing digital graphics objects having a stacking order. One method includes rasterizing the graphics objects by marking pixels in a pixel array, where each graphics object is separately rasterized according to a processing sequence that follows the stacking order from top to bottom; and, during the rasterization, tracking which pixels have been marked. Tracking which pixels have been marked can include using at least one tracking list that is associated with a scan line defining a sequence of pixels in a pixel array and that identifies marked or unmarked segments in the scan line. Rasterizing the graphics objects can include using the tracking list to identify markable pixels in the pixel array and marking only those pixels that are markable according to the tracking list. Marking pixels can include assigning any graphical attribute of a graphics object to the pixels.

Dependencies are inferred from the claim text.