This function converts the absolute path name given by path into a relative path name if possible. If the graphic file is in or below the same directory as the document doc, then a path name relative to the document directory is returned. If the file name is located within a directory given by the graphicspath option, or a subdirectory of a directory given by the graphicspath option, then the base name is returned. Otherwise, the input path name is returned.

If doc is zero or omitted, the current document is used.

This function is used by oid_set_graphic_pathname and insert_graphic_file functions when storing a graphic file reference.