Resources and References
This is a (likely incomplete) list of binary de-skew
developers. Other companies may incorporate their products on a
Many of the leading scanner manufacturers quietly
incorporate mechanical de-skew functions into their feeders and
transports. Those specifically discussed in this white paper are
As we note above, this technique is often
computationally expensive and unnecessary, since working with the
document's black border works so well. But it is interesting
technically, so we include some references.
Three good surveys of image-based skew measurement papers
- Witten, I. et al, 1994, Managing Gigabytes, Van
Nostrand Reinhold, New York, pp. 326-327.
- O'Gorman, L. and R. Kasturi, 1995, Document Image
Analysis, IEEE Computer Society Press, Los Alamitos,
CA, pp. 161-165.
- Amin, A. et al, "Comparative study of skew detection
algorithms," J. Electronic Imaging, 5:4, October
1996, pp. 443-451.
A list of some of the relevant papers follows.
- Postl,W., "Detection of linear oblique structures
and skew scan in digitized documents," Proc. 8th
Int'l. Conf. on Pattern Recognition, October, 1986,
- Baird, H.S., "The skew angle of printed
documents," Proc. Conf. Soc. Photographic Scientists
and Engineers, 1987, pp. 14-21.
- Hinds, S.C., J.L. Fisher, and D.P. D'Amato, "A
document skew detection method using run-length encoding
and the Hough transform," Proc. 10th Int'l. Conf.
Pattern Recognition (ICPR), June, 1990, pp. 464-468.
- J.L. Fisher, S.C. Hinds, and D.P. D'Amato, "A
rule-based system for document image segmentation,"
Proc. 10th Int'l. Conf. Pattern Recognition (ICPR), June,
1990, pp. 567-572.
- Nakano, Y., et al, "An algorithm for the skew
normalization of document image," Proc. 10th Int'l.
Conf. Pattern Recognition (ICPR), June, 1990, pp. 8-13.
- Story, G., et al, "The RightPages image-based
electronic library for alerting and browsing," IEEE
Computer, Sept. 1992, pp. 17-26.
- O'Gorman, L., "The document spectrum for page layout
analysis," IEEE Trans. Pattern Analysis and Machine
Intelligence, 15:11, Nov. 1993, pp. 1162-1173.