1. A method of generating a region-based representation of a document, the method comprising: generating an object-based representation of the document, the document comprising a plurality of objects; generating a global compositing sequence using fill data and a compositing operation associated with the plurality of objects independently of regions of overlap between the plurality of objects, the global compositing sequence being stored in a global compositing sequence store; and generating the region-based representation of the document using the object-based representation, the region-based representation comprising references to the global compositing sequence and a local compositing sequence, the local compositing sequence being stored in a local compositing sequence store, the local compositing sequence being determined on a per region basis based on objects contributing to a corresponding region, wherein the region-based representation comprises an indication of whether a region of the region-based representation references the global compositing sequence store or the local compositing sequence store to allow rendering of the region-based representation.