Skew detection in document images

摘要

Skew angle in a document image (A) is estimated using operators known from mathematical morphology. Skew angle in a document image (A) is estimated by run-length smoothing the image and then producing a plurality of eroded run-length-smoothed images. The run-length-smoothed image (RLSA(A)) is eroded using a linear structuring element (k2L alpha ) oriented at each of a plurality of different angles ( alpha ). The angle of the linear structuring element which produces an eroded image having the greatest surface area is designated as the skew angle. A plurality of run-length-smoothed images (RLSA alpha (A)) may be produced, each generated by smoothing the document image using a linear structuring element (k1L alpha ) oriented at a respective different angle ( alpha i). Then each run-length smoothed image (RLSA alpha (A)) is eroded using a linear structuring element oriented at the corresponding angle ( alpha i). <IMAGE>