1. A method for analyzing, using a data processing device, image data of an image that includes at least one object, to determine if at least one target object appears in the image, comprising: locating an object in the image data using the data processing device; extracting a contour of the object from the image data using the data processing device, the extracted contour having a plurality of points distributed along the contour, each point having relative location values associated with that point; generating a normalized contour from the extracted contour using the data processing device, the normalized contour having a determined number of normalized points distributed along the normalized contour, each normalized point having relative location values associated with that normalized point; determining, for each normalized point along the normalized contour, a value of a selected summation invariant for that normalized point using the data processing device; comparing, using the data processing device, for at least one target object, each target object having a corresponding target contour, each target contour having the determined number of points distributed along that target contour, each determined point having a value of the selected summation invariant associated with that determined point, the determined summation invariant values for the determined number of normalized points along the normalized contour to the determined summation invariant values for the determined number of points along the target contour corresponding to that target object; and determining, using the data processing device, based on the comparison to the at least one target object, if the located object sufficiently matches at least one of the at least one target object.