Townsend and Towsend and Crew
Image registration using projection histogram matching
 Image registration is performed by reducing images to histograms, rotating histograms to register the histograms, then using the registration of the histograms to register the images, thereby registering images with less computation than image rotation. Where the image is compressed using line-by-line run length encoding, the histogram can be derived from the run length encoding without decompression. Histogram rotation can also be used for skew angle detection. 
Ricoh Company, Ltd. Ricoh Corporation
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Jonathan J.
Hull