Patent ID: 7271814

Claim:
A method of blending a plurality of mutually overlapping graphical objects in a digital document processing system, wherein said plurality of graphical objects is arranged in an ordered stack, the order being that in which the objects are to be rendered, said stack including a plurality of static objects and at least one animated object, each of said objects comprising graphical content and having at least one blending parameter comprising at least one alpha value representing the transparency of at least part of the object associated therewith, the method comprising: (a) organizing the static objects into clusters comprising a first cluster of those static objects lying below the animated object in the ordered stack, and a second cluster of those static objects lying above the animated object in the ordered stack; (b) for each of said first and second clusters, blending the content of said static objects within the cluster to form first and second composite static objects, taking account of the respective blending parameters of the static objects; (c) blending the content of the animated object and the first and second composite static objects, taking account of the blending parameter(s) of the animated object to produce an image; (d) repeating step (c) using the previously obtained first and second composite static objects formed in step (b) when the content of the animated object changes to produce an undated image; and (e) storing or presenting to a user images produced in steps (c) and (d).