1. A method comprising: obtaining input image data defining an input image set that shows a graphical representation of a layout that includes two or more segments; the graphical representation including segment source information indicating sources of the segments in the layout and segment position information indicating positions of the segments within the layout; the segment source information including, for a first one of the segments, segment identifier marks indicating a segment identifier identifying the first segment; and using the input image data to obtain segment source data indicating a source for each of the segments and segment position data indicating a position for each of the segments; the act of using the input image data to obtain segment source data comprising: obtaining segment identifier data indicating the segment identifier indicated by the segment identifier marks; and using the segment identifier data to obtain the segment source data; the segment source data indicating a source for the first segment.