Image analysis – Image segmentation
Reexamination Certificate
1998-02-02
2001-09-11
Tran, Phuoc (Department: 2621)
Image analysis
Image segmentation
C382S170000
Reexamination Certificate
active
06289120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and system for image segmentation which is applicable to a document image processing system such as an Optical Character Recognition (OCR) system. This invention further relates to a method and system which is able to discriminate both a regular and irregular form area of a document image having a polygonal or complex structure. The invention is still further related to a method and system for determining whether characters are interior to or exterior to a form.
2. Discussion of the Background
As computers and image processing and forming systems become less expensive as technology improves, these systems become more popular and more accessible to the general public. The increasing popularity allows the image processing systems to become even more improved. An example of an improved image processing system is disclosed in U.S. Pat. No. 5,335,290 issued to Cullen et al., which is incorporated herein by reference. The system disclosed in Cullen et al. sets forth a technique of segmenting a document image into areas constituting text and areas which do not contain text. This system demonstrates features used in an image processing system such as compression of a bit-mapped image, and construction of a rectangle in order to process images.
In addition to classifying an image of a document into a text area and a non-text area, Japanese Laid-Open Patent Application 7-37036 published Feb. 7, 1995 discloses an image segmentation function which is used to classify a text area and a picture area of a document image using an image analysis technique. JP 7-37036 discloses the use of a circumscribing rectangle and a provisional ruled line which is extracted from the document image. The present invention has grown out of the system and process disclosed in JP 7-37036 and relies on some of the techniques disclosed in this patent. Specifically, portions of the present invention including at least parts of
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of the present application are based on techniques set forth in JP 7-37036. However, JP 7-37036 is based on the processing of a regular form image having a rectangular construction and difficulties would arise if JP 7-37036 attempted to process irregularly shaped forms.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to provide a new and useful method and system for processing images of forms having irregular construction.
Another object of this invention is to provide a document image processing system which improves the form area processing.
Yet another object of this invention is to provide a system which can determine if a document image has an irregularly shaped form and/or to determine this irregularly shaped form.
A still further object of this invention is to determine whether characters are interior to or exterior to a form, including forms which are irregularly and regularly shaped.
These and other objects are accomplished by a system and method according to the present invention which processes images. First, a rough classification of the images is performed in order to determine horizontal ruled line candidates, vertical ruled line candidates, and form candidates. The present invention classifies the form candidates into specific classes indicating whether the form candidate is a figure or other object, a graph, a surrounding frame, or a form. The form may or may not be a regularly shaped form.
When analyzing whether a form candidate image is an irregular form, a first core is constructed by first determining horizontal lines defining the core and then vertical lines. Also, a second core is constructed by first determining vertical lines defining the sides of the core and then horizontal lines defining the top and bottom of the core. Based on these two cores of the form candidate image being processed, whether or not the image contains an irregular form can be determined. If the image does not contain an irregular form, the image can be classified as a figure or other type of area, or as a graph. The conclusion that the form candidate contains a regular form can be reached either before the irregular form determination process or during the irregular form determination process, or alternatively after the irregular form determination process.
Another feature of the invention is determining whether characters are inside or outside of a form. This aspect of the invention is particularly helpful for irregularly shaped forms. The invention allows the determination of what constitutes an irregular area or form and what constitutes characters outside of the form. With this proper classification performed, an optical character recognition (OCR) process can be performed on images of characters interior to an irregular form. Without the form of a cell outside of the form, it may be difficult to perform an OCR process outside of the form, although the present invention can perform an OCR process on images of characters which are either interior to or exterior to a form. Prior art systems cannot determine cells which are part of an irregularly shaped form and therefore, cannot perform an OCR process for these forms as the cell cannot be determined.
REFERENCES:
patent: 4850025 (1989-07-01), Abe
patent: 4933984 (1990-06-01), Nakaano et al.
patent: 5101448 (1992-03-01), Kawachiya et al.
patent: 5191612 (1993-03-01), Katsuyama
patent: 5228100 (1993-07-01), Takeda et al.
patent: 5335290 (1994-08-01), Cullen et al.
patent: 7-37036 (1995-02-01), None
Saitoh Takashi
Yamaai Toshifumi
Yamada Masanori
Alavi Amir
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Tran Phuoc
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