Methods, systems, apparatus, and computer program products involve modifying graphic objects. An electronic document can be obtained in a first format. The electronic document can include a graphic object represented using a main dataset and a private dataset. The main dataset can be normalized while stored in an object model in memory. A checksum can be computed for the normalized main dataset of the graphic object. The computed checksum can be compared with a stored checksum located in the electronic document. The electronic document can be converted from the first format to a second format based in part on a result of the comparison.