Method for emphasizing differences in graphical appearance between an original document and a modified document with annotations including outer and inner boundaries

A method for emphasizing differences in graphical appearances between an original document and a modified document with attached annotations, the method comprising:

• receiving a first bitmap of the modified document and a second bitmap of the original document;
• deriving a set of difference points based upon a comparison of the first bitmap and the second bitmap, the difference points being representative of coordinates within the first and second bitmaps having pixel value differences exceeding a predetermined threshold;
• deriving from the set of difference points an outer boundary defined by a first subset of polygon vertices;
• setting a hollow interior classification flag based upon a calculated density of a second subset of the polygon vertices being below a predetermined threshold;
• deriving from the set of difference points one or more inner boundaries defined by one or more groups of the second subset of the polygon vertices when the hollow interior classification flag is set;
• and
• generating an annotation defined by an area between the outer boundary and the one or more inner boundaries.