15. The apparatus according to claim 14 , wherein the first requirement includes a parameter range showing the range of an element parameter that indicates properties of a graphic to be selected as a ruled line element of the ruled line and/or the range of a consolidation parameter that indicates properties of the graphic of the ruled line element to be consolidated as ruled line candidate.
16. The apparatus according to claim 15 , wherein the extraction section is adapted to select a graphic that makes the element parameter to be found within the corresponding parameter range from the document image and consolidate a plurality of ruled line elements that make the consolidation parameter to be found within the corresponding parameter range to generate the ruled line candidate.