Consider adding DPI info via page property 'scan_res'
http://kba.cloud/hocr-spec/1.2/#propdef-scan_res
Could be useful for PDF generation -- although we can likely also get it via item info and scandata
http://kba.cloud/hocr-spec/1.2/#propdef-scan_res
Could be useful for PDF generation -- although we can likely also get it via item info and scandata