EP0800148B1
Expired / Lapsed
EP
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Image processing system
Assignee: HP Inc
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Filing: 1997-04-02
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Granted: 2002-07-17
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Expires: 2017-04-02
Abstract
No abstract record available.
Inventors
- 👤 Daniel R. Tretter
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 10:41
CPC Classifications
G; G06; G06T; G06T3/00; G06T3/60; G06T3/606
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
253 words
A method of determining a skew angle (α) of a document image (301,
401) inside a scan image (300, 400) having a plurality of scan lines of pixels,
comprising the steps of: (A) receiving a scan line of pixels of the scan image (300, 400); and (B) automatically detecting an edge segment (304, 306) of the document
image by detecting a first/last document image pixel (311-314, 411, 412) of the scan
line of pixels that belongs to the document image (301, 401) without dividing the scan
fine into a number of multiple-pixel blocks and without any user intervention and input; characterised by the following steps: (C) if the first/last document image pixel (311-314, 411, 412) of the scan line
continues the edge segment (304, 306) having the first/last document image pixel of
previous scan lines of the scan image (300, 400), then automatically extending the edge
segment (304, 306) to the first/last document image pixel (311-314, 411, 412) of the
scan line; (D) repeating the steps of (A) to (C) until the edge segment (304, 306)
cannot be further extended without any user intervention and without requiring that the
document image (301, 401) contains text, wherein the edge segment (304, 306) forms
an edge of the document image (301, 401); (E) determining if the edge segment (304, 306) is longer than a
predetermined length value; and (F) determining the skew angle (α) by determining a slope of the edge
segment (304, 306) if the edge segment is longer than the predetermined length value.
Claim 2
Dependent Claim
95 words
The method of claim 1, wherein the scan image (300, 400) includes
document image pixels of the document image (301, 401) and background pixels of the
scan image (300, 400), wherein the step (B) further comprises the steps of: (I) receiving a corresponding scan line of predetermined background pixels; (II) comparing the scan line of pixels of the scan image (300, 400) with the
corresponding scan line of predetermined background pixels to locate the first/last
document image pixel (311-314, 411, 412) of the scan line of pixels that belongs to the
document image (301, 401).
Claim 3
Dependent Claim
120 words
The method of claim 2, wherein the step (II) comprises the steps of: comparing colour of the first/last document image pixel (311-314, 411, 412)
with colour of its corresponding background pixel; comparing colour of an adjacent pixel of the first/last document image pixel
(311-314, 411, 412) with colour of its corresponding background pixel; determining that the first/last document image pixel (311-314, 411, 412) is
indeed the first/last document image pixel (311-314, 411, 412) of the document image
(301, 401) along the scan line if the colour of the first/last document image pixel (311-314,
411, 412) is different from that of its corresponding background pixel and the
colour of the adjacent pixel is different from that of its corresponding background pixel.
Claim 4
Dependent Claim
77 words
The method of claim 1, wherein the step (F) comprises the steps of: (a) determining if the document image (301, 401) has a rectangular shape by
determining (1) if the edge segment (305) is perpendicular or parallel to previous edge
segments (304, 307) and (2) if the edge segment (305) is longer than the predetermined
length value; (b) setting the skew angle (α) to zero if the document image (301, 401) does
not have the rectangular shape.
Claim 5
Dependent Claim
19 words
The method of claim 1 or 4, wherein the predetermined length value is
approximately equal to twenty five pixels.
Claim 6
Dependent Claim
150 words
The method of claim 1, comprising the steps of: checking each of the scan lines against a predetermined scan line of background pixels
to locate (1) a first document image pixel (311, 411) and a last document image pixel
(312, 412) for a first scan line of the scan lines, (2) a first document image pixel (315, 415) and a last document image pixel
(316, 416) of a last scan line of the scan lines; (3) a leftmost image pixel (313, 413) of the document image; and (4) a rightmost document image pixel (314, 414) of the document image; connecting the first and last document image pixels (311, 312, 315, 316, 411,
412, 415, 416) of the first and last scan lines, the leftmost document image pixel (313,
413), and the rightmost document image pixel (314, 414) together to define the
boundary (301a, 400a) of the document image (301, 401).
Claim 7
Dependent Claim
20 words
The method of claim 6, comprising the step of determining if the
document image (301, 401) has multiple skew angles.
Claim 8
Dependent Claim
104 words
The method of claim 7, comprising the step of extending (1) a first
horizontal line through the first and last document image pixels (311, 312, 411, 412) of
the first scan line, (2) a second horizontal line through the first and last document image
pixels (315, 316, 415, 416) of the last scan line, (3) a first vertical line through the
leftmost document image pixel (313, 413), and (4) a second vertical line through the
rightmost document image pixel (314, 414) to define the boundary (301a, 400a) of the
document image (301, 401) if the document image (301, 401) has multiple skew angles .
References Cited (Backward Citations)
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