US5054098A — Method of detecting the skew angle of a printed b…

Claim 1

Independent Claim 366 words

A method for reliably determining the skew angle of a scanned digitized document image in a computer comprising the steps of: thresholding the digitized image to produce a binary image; converting the binary image into a collection of closed polygons formed by a series of vectors using contour vectorization; determine the width and height of an encompassing rectangle for each polygon; establish a threshold using either the height or width of the rectangle to separate all the polygons into two categories with a first category containing small polygons having either heights or widths smaller than a predetermined value and the second category of larger polygons wherein either the height or width is greater than a predetermined second value; transforming the vectors of each polygon in the second category of polygons employing a modified Hough transform which includes a) determining the center coordinates of each vector in a given polygon from the second category of large polygons; b) calculating the length and angle (Θ) of each vector; c) using the center coordinates and the angle of each vector in each polygon to determine the value of p in parametric space, using p=x cos Θ+sine Θ and plot the histogram of (p, Θ) using vector length for each vector in said polygon; d) include on said plot of the histogram all vector lengths for all vectors in a polygon in a cumulative fashion; e) detecting the peaks that exist at Θ 1 in the parametric domain and determine if corresponding peaks exist at Θ 1 +180°; and f) repeat the steps a-e until all the large size polygons in the second category have been processed; detecting peaks in the histogram in the parametric domain using a predetermined third threshold; determining the angular value Θ of the peak values above said third threshold; determining if any angular values Θ 1 have additional corresponding peaks at Θ 1 at 180° and if so determined, average all values of Θ 1 so determined and the average value Θ 1 will be defined as the skew angle of the document; and rotate the digitized document image in the computer by Θ 1 degrees to properly orient the document image for further processing.

Claim 2

Independent Claim 366 words

A method for reliably determining the skew angle of a scanned digitized document image in a computer comprising the steps of: thresholding the digitized image to produce a binary image; converting the binary image into a collection of closed polygons formed by a series of vectors using contour vectorization; determine the width and height of an encompassing rectangle for each polygon; establish a threshold using either the height or width of the rectangle to separate all the polygons into two categories with a first category containing small polygons having either heights or widths smaller than a predetermined value and the second category of larger polygons wherein either the height or width is greater than a predetermined second value; transforming the vectors of each polygon in the second category of polygons employing a modified Hough transform which includes a) determining the center coordinates of each vector in a given polygon from the second category of large polygons; b) calculating the length and angle (Θ) of each vector; c) using the center coordinates and the angle of each vector in each polygon to determine the value of p in parametric space, using p=x cos Θ+sine Θ and plot the histogram of (p, Θ) using vector length for each vector in said polygon; d) include on said plot of the histogram all vector lengths for all vectors in a polygon in a cumulative fashion; e) detecting the peaks that exist at Θ 1 in the parametric domain and determine if corresponding peaks exist at Θ 1 +180°; and f) repeat the steps a-e until all the large size polygons in the second category have been processed; detecting peaks in the histogram in the parametric domain using a predetermined third threshold; determining the angular value Θ of the peak values above said third threshold; determining if any angular values Θ 1 have additional corresponding peaks at Θ 1 at 180° and if so determined, average all values of Θ 1 so determined and the average value Θ 1 will be defined as the skew angle of the document; and rotate the digitized document image in the computer by Θ 1 degrees to properly orient the document image for further processing.

Claim 3

Dependent Claim 37 words

The method of determining skew angle of a digitized document image in a computer as set forth in claim 1 wherein said contour vectorization is comprised of the steps of contour pixel tracing and piecewise linear approximation.

Claim 4

Dependent Claim 39 words

The method of determining skew angle of a digitized document image in a computer as set forth in claim 2 wherein the center coordinates of the rectangle that encompasses the polygon is used as the origin of the Cartisean

Claim 5

Dependent Claim 32 words

The method of determining skew angle as set forth in claim 3 wherein ρ is the length of the line from the origin normal to the vector in the Cartisean coordinate system.

Claim 6

Dependent Claim 331 words

A polygon based method for determining the skew angle of a scanned digitized form document image in a computer comprising the steps of: a) thresholding the digitized image to produce a binary image; b) use contour vectorization to convert the binary image into a collection of closed polygons formed by a series of vectors; c) determining the width and height for an encompassing rectangle that encompasses the polygon; d) establish a threshold to separate all the polygons into two categories with the first category including smaller polygons that have either the height or width of an encompassing rectangle less than a predetermined value and the second category containing larger polygons having either the height or width of an encompassing rectangle larger than a predetermined value; e) determining the center coordinates of each vector in each polygon from the second category or larger polygons; f) determine the length and angle of each vector; g) using said center coordinates and said angle of each vector in each polygon to determine the value of ρ in parametric space using ρ=X cos Θ+Y sin Θ and plot the histogram of (ρ,Θ) using the vector length for each vector in said polygon; h) include on the plot of the histogram all vector lengths for all vectors in each polygon in a cumulative fashion; i) detecting the peaks that exist in the parametrix domain and determine a corresponding value for Θ; j) repeat the steps e-i until all the larger size polygon having heights or widths of an encompassing rectangle greater than said predetermined value have been processed; k) determine the angular values of the peaks above a predetermined threshold; l) determine if any of the specifically determined angular values Θ 1 have corresponding angular values at Θ 1 +180° and if so determined define Θ 1 as the skew angle of the document; and m) rotate the digitized document image in the computer by Θ 1 degrees to properly orient the document image for further processing.

Claim 7

Dependent Claim 331 words

A polygon based method for determining the skew angle of a scanned digitized form document image in a computer comprising the steps of: a) thresholding the digitized image to produce a binary image; b) use contour vectorization to convert the binary image into a collection of closed polygons formed by a series of vectors; c) determining the width and height for an encompassing rectangle that encompasses the polygon; d) establish a threshold to separate all the polygons into two categories with the first category including smaller polygons that have either the height or width of an encompassing rectangle less than a predetermined value and the second category containing larger polygons having either the height or width of an encompassing rectangle larger than a predetermined value; e) determining the center coordinates of each vector in each polygon from the second category or larger polygons; f) determine the length and angle of each vector; g) using said center coordinates and said angle of each vector in each polygon to determine the value of ρ in parametric space using ρ=X cos Θ+Y sin Θ and plot the histogram of (ρ,Θ) using the vector length for each vector in said polygon; h) include on the plot of the histogram all vector lengths for all vectors in each polygon in a cumulative fashion; i) detecting the peaks that exist in the parametrix domain and determine a corresponding value for Θ; j) repeat the steps e-i until all the larger size polygon having heights or widths of an encompassing rectangle greater than said predetermined value have been processed; k) determine the angular values of the peaks above a predetermined threshold; l) determine if any of the specifically determined angular values Θ 1 have corresponding angular values at Θ 1 +180° and if so determined define Θ 1 as the skew angle of the document; and m) rotate the digitized document image in the computer by Θ 1 degrees to properly orient the document image for further processing.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-09-30	1995-04-01	1995-10-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-09-30	1999-04-01	1999-10-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-09-30	2003-04-01	2003-10-01	$7700.00	Window Closed / Lapsed

Method of detecting the skew angle of a printed business form

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag