1. A method for determining positions of images of a stroke, comprising: grouping a plurality of images of a stroke in a document into one or more segments, such that each segment has a first located image corresponding to a first known position in the document and a last located image corresponding to a second known position in the document; determining if each segment is finished or unfinished, each finished segment including at least a third located image corresponding to a third known position in the document; and finishing each unfinished segment.