EP0949802A2
Expired / Lapsed
EP
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Image processing system with image cropping and skew correction
Assignee: HP Inc
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Filing: 1999-04-06
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Granted: —
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Expires: 2019-04-06
Abstract
Abstract A system and method is described for automatically determining in a scanned document image 500 the presence of unwanted extraneous information caused by an extraneous device and scanner background information 504. Once the presence of this information is determined, the system and method of the present invention can compute, for instance, skew and crop statistics. From this, the image 500 can be automatically deskewed and cropped 322 appropriately without the background and extraneous information 504. The system and method accomplishes this by first determining the presence of unwanted extraneous and background information 504 and then appropriately processing the document image 500. The extraneous information 504 is ignored during deskew and crop computations. Also, the scanner background and the extraneous information 504 are prevented from being included in the final digital representation of the image 600.
Inventors
- 👤 Cindy Y. Sansom-Wai
- 👤 Irene H. Williams
- 👤 Daniel R. Tretter
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 10:12
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/387; H04N1/3877; H04N1/3878; G; G06; G06V; G06V10/00; G06V10/20; G06V10/24; H04N1/38; H04N1/3872; H04N1/3873
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
115 words
A method of determining a skew angle of a document image 502 inside a
scan image 500 having a plurality of scan lines 1100 of pixels 1070, comprising: (A) successively receiving scan lines 1100 of pixels 1070 of the scan image
500; (B) comparing a neighborhood of pixels located around a group of scan lines
1100 with predetermined background pixels 1080 to define left and right image boundaries
for each group of scan lines 1100; (C) forming an edge segment 1102 by extending an image boundary between
successive groups of scan lines 1100; and (D) determining the skew angle by calculating an aggregate slope of all edge
segments 1102 longer than a predetermined length value.
Claim 2
Dependent Claim
30 words
The method of claim 1 further comprising, after step (A) and before step
(B), searching for known characteristics within the document image 502 and ignoring the
known characteristics if found.
Claim 3
Dependent Claim
81 words
The method of claim 1, wherein the scan image includes document image
pixels 1070 of the document image 502 and background pixels 1080 of the scan image
500, wherein the step (B) further comprises: (I) receiving a neighborhood of pixels located around a group of scan lines
1100; and (II) comparing the group of scan lines 1100 of the scan image 500 with
corresponding background pixels 1080 to define left and right image boundaries for each
group of scan lines 1100.
Claim 4
Dependent Claim
63 words
The method of claim 1, wherein step (C) further comprises: (I) ending the edge segment 1102 and generating a new edge segment 1202
that extends from an end scan line of the group of scan lines 1100 if the group of scan
lines 1100 do not continue the edge segment; and (II) repeating steps (A), (B) and (C) a predetermined number of times.
Claim 5
Independent Claim
160 words
A method of determining a boundary of a document image 502 inside a
scan image 500 having a plurality of scan lines 1100 of pixels 1070, comprising: (A) checking a neighborhood of pixels located around a group of scan lines
1100 against predetermined background pixels 1080 to locate, (1) a first document image pixel 518 and a last document image pixel
520 for a first scan line of the scan lines, (2) a first document image pixel 524 and a last document image pixel
526 of a last scan line of the scan lines, (3) a leftmost document image pixel 521 of the document image 502,
and (4) a rightmost document image pixel 522 of the document image; (B) connecting the first 518, 524 and last 520, 526 document image pixels of
the first and last scan lines, the leftmost document image pixel, and the rightmost
document image pixel 522 together to define the boundary of the document image 502.
Claim 6
Dependent Claim
17 words
The method of claim 5, further comprising determining if the document
image 502 has multiple skew angles.
Claim 7
Dependent Claim
89 words
The method of claim 6, further comprising extending (1) a first horizontal
line through the first 518 and last 520 document image pixels of the first scan line, (2) a
second horizontal line through the first 524 and last 526 document image pixels of the last
scan line, (3) a first vertical line through the leftmost document image pixel, 521 and (4) a
second vertical line through the rightmost document image pixel 522 to define the
boundary of the document image if the document image has multiple skew angles.
Claim 8
Independent Claim
178 words
An apparatus, comprising: (A) a storage medium 208; (B) a computer executable program 322 stored on the storage medium 208,
the computer executable program 322, when executed, determining a skew angle of a
document image 502 inside a scan image 500 having a plurality of scan lines 1100 of
pixels 1070, wherein the computer executable program 322comprises, (I) a first set of instructions that receives and examines a
neighborhood of pixels located around a group of scan lines 1100 of pixels 1070 of the
scan image 500; (II) a second set of instructions that compares a neighborhood of pixels
located around a group of scan lines 1100 with predetermined background pixels 1080 to
define left and right image boundaries for each group of scan lines 1100; (III) a third set of instructions that forms an edge segment 1102 by
extending an image boundary between continuous groups of scan lines 1100; and (IV) a fourth set of instructions that determines the skew angle by
calculating the aggregate slope of all edge segments 1102 longer than a predetermined
length value.
Claim 9
Dependent Claim
173 words
The apparatus of claim 8, wherein the scan image includes image pixels
1070 of the document image 502 and background pixels 1080 of the scan image 500,
wherein the second set of instructions further comprises, (a) a first subset of the second set of instructions that receives a neighborhood
of pixels located around a group of scan lines 1100; (b) a second subset of the second set of instructions that compares color of
the group of scan lines 1100 with color of the corresponding background pixels 1080; (c) a third subset of the second set of instructions that compares color of
adjacent pixels of the group of scan lines 1100 with color of the corresponding background
pixels 1080; and (d) a fourth subset of the second set of instructions that confirms the location
of an image boundary when the color of the group of scan lines 1100 is different from that
of the corresponding background pixels and the color of the adjacent pixels are different
from that of the corresponding background pixels 1080.
Claim 10
Independent Claim
83 words
A method for automatically deskewing a scanned document image 502,
comprising: generating an electrical signal indicative of a plurality of edge segments
1102 defining an image boundary of the scanned document image 502; calculating an aggregate slope of those individual ones of said plurality of
edge segments 1102 exceeding a predetermined length value, said aggregate slope being
indicative of the skew angle of the scanned document 502; and rotating a digital representation of the scanned document image 502 by the
determined skew angle.
References Cited (Backward Citations)
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