Document skew detection/control system for printed document images containing a mixture of pure text lines and non-text portions
First Claim
1. An apparatus for determining a skew angle of an input document that contains at least a plurality of lines of text characters and a non-text portion, said apparatus comprising:
- input means for generating an image of the input document;
detection means coupled to said input means for detecting a skew angle of said plurality of lines of text characters, comprising means for extracting at least one region including only text lines from the document with respect to a plurality of scanning lines which across the document image at selected angles that vary intermittently from a reference angle, means for computing complexity at each of angles, means for finding out a characteristic parameter in a distribution of the parameters in the region, and means for determining a corresponding angle, at which said characteristic parameter appears, as the skew angle of the input document; and
output means coupled to said detection means for generating a signal indicative of the skew angle thus determined.
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Abstract
A document skew detection apparatus for facilitating the recognition of the contents of a printed document includes an image processing section for generating a binary coded image of the document containing a plurality of black picture elements distributed among white picture elements to depict pure text lines and non-text portions of the document. The binary coded image is then modified so that certain ones of the black picture elements satisfying a predetermined condition are integrated together to generate a coarse document image being decreased in resolution. The apparatus also includes an image extraction section for extracting from the document image a local image region containing pure text lines occupying an almost entire area thereof, and skew detection section for detecting a direction of orientation of the text lines of the local region, and for determining an angular difference between a detected direction and a reference direction as a skew angle of the printed document.
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Citations
18 Claims
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1. An apparatus for determining a skew angle of an input document that contains at least a plurality of lines of text characters and a non-text portion, said apparatus comprising:
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input means for generating an image of the input document; detection means coupled to said input means for detecting a skew angle of said plurality of lines of text characters, comprising means for extracting at least one region including only text lines from the document with respect to a plurality of scanning lines which across the document image at selected angles that vary intermittently from a reference angle, means for computing complexity at each of angles, means for finding out a characteristic parameter in a distribution of the parameters in the region, and means for determining a corresponding angle, at which said characteristic parameter appears, as the skew angle of the input document; and output means coupled to said detection means for generating a signal indicative of the skew angle thus determined. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A document skew determination tool for facilitating the recognition of the contents of a printed document comprising the steps of:
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generating a binary coded image of the document containing a plurality of black picture elements distributed among white picture elements to depict pure text lines and non-text portions of the document; modifying the binary coded image so that certain ones of the black picture elements satisfying a predetermined condition are integrated together to generate a coarse document image being decreased in resolution; extracting a local region from the document image, said local region containing pure text lines occupying an almost entire area thereof; detecting a direction of orientation of the text lines in said local region; and determining an angular difference between a detected direction and a reference direction as a skew angle of the printed document. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification