Abstract: A method is described of compositing graphic elements in a pixel-based renderer (18). A first graphic element is received (step 2601) having a first colour and a first opacity and a second graphic element is received (step 2602) having a second colour and a second opacity. A blend output is obtained from a blend function dependent on the first colour and the second colour; and a resultant colour is determined (step 2603) of a compositing operation on the first and second graphic elements, the resultant colour being dependent on the blend output and otherwise being independent of the second colour.

Abstract: A mixed text and image layout algorithm capable of supporting Unicode text and arbitrary content definitions for geometric layout with worst case two-pass layout placement procedure. Layout of Unicode text requires a number of distinct processing steps commencing with classification of input characters into contiguous groups of identical directionality, writing system and possibly script (and language) followed by mapping of character groups to glyphs for display purposes followed by a layout taking into account font display characteristics, embedded directionality level and shape of container for layout contents. Layout is best-case achieved in a single layout pass and worst-case in two passes. During layout information is cached to facilitate incremental changes to an existing layout in order to minimize refresh operations for editing display purposes. An optional two-pass operation on the layout result may be used to generate ordered rendering operation to support so-called Z-index display.

Abstract: A method (1000) of compositing a group of graphical objects (B). The method (1000) forms the group of objects (B) in a temporary buffer (W). For each object (C, D) in the group of objects (B), a corresponding clipping path is provided. A resultant clipping path (Z) defined by a union of the clipping paths is calculated. The group of objects from the temporary buffer (W) is composited to a main buffer (V) through the resultant clipping path (Z).