Merge pull request #5 from adam-vessey/7.x

Add check for existence of function, before trying to call it.
Updating default hocr dsid.
xpath change, better hocr
Merge pull request #6 from willtp87/7.x

Updating default hocr dsid.
Allow the use of height/width stored in RELS-INT.
Generate dimensions for JP2 derivatives, and put into RELS-INT.