JPH1153469A - Character segmentation device, optical character reader and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical character reader capable of recognizing characters highly precisely. SOLUTION: The superimposing of plural character circumscribing rectangles for respectively indicating character components is detected in a superimposing boundary detection part 15. A superimposing boundary correction part 16 sets a superimposing boundary area between the character circumscribing rectangle and the character circumscribing rectangle adjacent to it for which the superimposing is detected, specifies the character circumscribing rectangle to which a line segment circumscribing rectangle present inside the area is to belong and adds the coordinate information of the line segment circumscribing rectangle to the pertinent character circumscribing rectangle. A pattern extraction part 14 extracts (segments) the character pattern of the area indicated by the coordinate information of the circumscribing rectangle and the line segment circumscribing rectangle from an image memory 11 and preserves it in a pattern memory 17. A character recognition part 18 performs the recognition processing of the character pattern inside the pattern memory 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character recognition technique based on an optical technique, and more particularly to a technique for efficiently cutting out and reading a character pattern in an area of a frameless ruled line frame (free pitch frame). .

[0002]

2. Description of the Related Art An optical character reader (OC) which scans a character printed or handwritten on a form or the like by optical means, cuts out an image of the character, and automatically recognizes it.
R: Optical Character Reader) is known.

FIG. 5 is a functional block diagram of a conventional OCR of this kind. The OCR 5 has an image memory 11,
It includes a circumscribed rectangle extracting unit 12, a circumscribed rectangle integrating unit 13A, a pattern extracting unit 14, a pattern memory 17, and a character recognizing unit 18, and is in a free pitch frame in an image image of a form (hereinafter, form image), for example. Character recognition is performed by extracting characters. The character extracting device is configured by the circumscribed rectangle extracting unit 12, the circumscribed rectangle integrating unit 13A, the pattern extracting unit 14, and the pattern memory 17.

[0004] The image memory 11 stores a form image input from optical scanning means such as a scanner (not shown). The circumscribed rectangle extracting unit 12 extracts a circumscribed rectangle (referred to as a line segment circumscribed rectangle) surrounding the connected area of the black pixels from the form image in the image memory 11. More specifically, a plurality of closed regions to which black pixels are connected are specified from the form image in the image memory 11, and the starting point coordinates of the smallest rectangle capable of surrounding the connected region of black pixels in each closed region. The coordinates of the end points are calculated to determine the circumscribed rectangle of the line segment. The determined plurality of line segment circumscribed rectangles are input to the circumscribed rectangle integration unit 13A.

The circumscribed rectangle integrating unit 13A integrates a plurality of line segment circumscribed rectangles input from the circumscribed rectangle extraction unit 12 in a first direction (for example, a vertical direction) and a character width in a second direction (for example, a horizontal direction). Is performed, the line segment circumscribed rectangle after integration is divided in the second direction, and a circumscribed rectangle surrounding the character pattern is created (referred to as a character circumscribed rectangle). The created character circumscribed rectangle is sequentially input to the pattern extraction unit 14 from the one corresponding to the first character.

[0006] The pattern extraction unit 14 is provided in the image memory 11.
The character pattern in the area corresponding to the coordinate information of the character circumscribed rectangle is extracted from the above form image and stored in the pattern memory 17. The character recognition unit 18 performs character recognition of the character pattern in the pattern memory 17 and outputs a recognition result to an output unit (not shown).

Next, the operation of the OCR 5 will be specifically described. For convenience, it is assumed that a form image including the character string “Tokyo” is stored in the image memory 11 as shown in FIG. This form image is a part of a field provided with a character frame. In the XY coordinate system, the X-axis direction is a horizontal direction (second direction) and the Y-axis direction is a vertical direction (first direction). It has been set.

The circumscribed rectangle integrating unit 13A integrates line segment circumscribed rectangles based on the following criteria. First, the length “a” of the overlapping portion of two target line segment circumscribed rectangles and the smaller length “b” of each line segment circumscribed rectangle are determined. Next, “a / b” is calculated, and it is determined whether or not the calculated value is equal to or greater than a predetermined line segment circumscribed rectangle integration threshold th1. If the calculated value is equal to or greater than the integration threshold th1, the result is integrated into a primary circumscribed rectangle, and if the calculated value is less than the integration threshold, the integration is not performed. FIG. 7 (a)
Is a schematic diagram in this case, and FIG. 7 (b) shows an example of a primary circumscribed rectangle obtained by integrating the two circumscribed rectangles shown in FIG. 7 (a). The circumscribed rectangle integrating unit 13A also estimates the standard character width sw from the created primary circumscribed rectangle. The standard character width sw in this case is, for example, the average of the widths of the line circumscribed rectangles included in the primary circumscribed rectangle. Bounding rectangular integration unit 13A
Performs a horizontal division of the primary circumscribed rectangle based on the standard character width sw. For example, the ratio "wi /" of the measured width wi of the primary circumscribed rectangle shown in FIG.
If sw "is equal to or greater than a predetermined division threshold th2, the primary circumscribed rectangle is divided into a plurality of character circumscribed rectangles.

FIG. 8 is a diagram showing an example of a primary circumscribed rectangle divided into three character circumscribed rectangles corresponding to "Tokyo". The character circumscribed rectangle can be represented by the start point coordinates and end point coordinates of the smallest rectangle surrounding each character equivalent area.
In the example of FIG. 8, the character circumscribed rectangle in the first character "East" has a start point coordinate of (X1, Y1) and an end point coordinate of (X2, Y
2), the character circumscribed rectangle of the second character “K” has a start point coordinate of (X3 (<X2), Y3) and an end point coordinate of (X
4, Y4), the character circumscribed rectangle in the final character “To” is
The start point coordinates are (X5 (<X4), Y5) and the end point coordinates are (X5
6, Y6). These coordinate information are
The corresponding character circumscribed rectangle is passed to the pattern extraction unit 14 in association with the corresponding character.

The pattern extracting section 14 extracts character patterns "East", "K", and "Miya" of the corresponding area from the image memory 11 based on the coordinate information of each character circumscribed rectangle, and extracts these in the order of extraction. 17 is stored. FIGS. 9A, 9B, and 9C show examples of cut-out character patterns.
Shown in In the example shown in FIG. 9, overlapping occurs for each character circumscribed rectangle. In such a case, simply cutting out the character pattern in the area corresponding to the coordinate information of the character circumscribed rectangle may cause intrusion of a line segment by an adjacent character,
This leads to a reduction in character recognition accuracy. Therefore, conventionally, a process for removing the invading line segment is performed in the pattern extraction unit 14. That is, as shown in FIG.
The character line boundaries a1 and a2 are set on the individual character circumscribed rectangles.
Is set as the end point, the boundary of the invading line segment is traced as shown in the figure, and white spotting is performed so as to remove the inside of the trace range on the pattern memory 17. After correcting the character pattern on the pattern memory 17 in this way, the character recognition unit 18
Perform character recognition.

[0011]

As described above, in the conventional OCR5, when overlapping of character circumscribed rectangles occurs, simply cutting out a character pattern corresponding to the character circumscribed rectangle will result in an adjacent character circumscribed rectangle. , A line segment is invaded, thereby lowering the character recognition accuracy.

In the case of removing the penetrated line segment,
Extra processing time is required at least for tracing the character line boundary. Further, conventionally, even in the case where the intrusion frequency of the line segment is low, the line segment including the trace is removed, so that it takes time until the character recognition is started, which is the processing speed of the entire OCR. Had been reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved character extracting device capable of quickly extracting a character pattern used for character recognition. Another object of the present invention is to provide an optical character reader and a character cutout device that can perform high-speed character recognition processing while maintaining the character recognition accuracy at a certain value or more, and a recording method for realizing the character cutout device with a general-purpose computer device. To provide a medium.

[0014]

A character segmenting apparatus according to the present invention for solving the above problems extracts a line segment circumscribed rectangle from an image including a plurality of character patterns, and converts the extracted line segment circumscribed rectangle in a first direction. A character circumscribed rectangle creating means for creating a plurality of character circumscribed rectangles by integrating and dividing the combined line segment circumscribed rectangle in a second direction perpendicular to the first direction;
Superimposition detection that determines whether the difference between one end point coordinate and the other start point coordinate of a pair of character circumscribed rectangles adjacent in the direction is equal to or greater than a predetermined superimposition detection threshold, and specifies a character cutout area of a size according to the determination result Means, and pattern extracting means for extracting a corresponding character pattern from the image based on output information of the superimposition detecting means.

In the above-described character segmentation apparatus, for example, when the difference is less than the overlap detection threshold, the superimposition detecting means designates coordinate information of an individual circumscribed rectangle as the character segmentation area. Is greater than or equal to the superimposition detection threshold, the size of each character circumscribed rectangle is changed to a size that avoids superimposition with other character circumscribed rectangles, and the coordinate information of the line segment circumscribed rectangle existing in the difference area and the line segment circumscribed rectangle And the coordinate information of a character circumscribed rectangle to which the character belongs. The difference area is automatically set based on a predetermined margin value.

According to another aspect of the present invention, there is provided an optical character reading apparatus for storing an image including a plurality of character components read by an optical scanning means, and storing the image in the image memory. A plurality of line segment circumscribed rectangles are extracted from the extracted image, the extracted line segment circumscribed rectangles are integrated in a first direction, and the combined line segment circumscribed rectangles are integrated in a second direction perpendicular to the first direction. A character circumscribed rectangle creating means for creating a plurality of character circumscribed rectangles by dividing, and a difference between one end point coordinate and the other start point coordinate of the pair of character circumscribed rectangles adjacent in the second direction is equal to or more than a predetermined superimposition detection threshold value Determining whether a character cutout area of a size corresponding to the determination result is provided, and extracting a corresponding character pattern from the image based on output information of the superimposition detection means. Consisting includes a pattern extracting unit, a character recognition means for performing character recognition based on the extracted character patterns, the.

Further, a recording medium according to the present invention for solving the above-mentioned other problems is a computer-readable recording medium in which a program for causing a computer to execute the following processing is recorded. (1) a process of extracting a line segment circumscribed rectangle from an image including a plurality of character patterns; (2) integrating the extracted line segment circumscribed rectangle in a first direction, and extracting the line segment circumscribed rectangle after integration in the first direction (3) a process of creating a plurality of character circumscribed rectangles by dividing in a second direction perpendicular to the first direction, and (3) determining a difference between one end point coordinate and the other start point coordinate of a pair of character circumscribed rectangles adjacent in the second direction. (4) When the difference is less than the superimposition detection threshold, the coordinate information of each circumscribed rectangle is designated as a character cutout area. If the detection threshold value or more, each character circumscribed rectangle should be changed to a size that avoids overlapping with another character circumscribed rectangle, and the coordinate information of the line circumscribed rectangle existing in the difference area and the line circumscribed rectangle should belong Character circumscribed square Processing for specifying the index information as a character cutout region, (5) on the basis of the specified coordinates information cutting out a character pattern corresponding from the picture image processing.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of an optical character reading device (OCR) provided with a character cutout device of the present invention. O of this embodiment
The CR1 is formed by a computer device reading and executing a predetermined program, and is formed by an image memory 11, a circumscribed rectangle extraction unit 12, a circumscribed rectangle integration unit 13, a pattern extraction unit 14, a superimposition boundary detection unit 15, a superimposition boundary correction. A circumscribed rectangle extraction unit 12, a circumscribed rectangle integration unit 13, a pattern extraction unit 14, a superimposed boundary detection unit 15, and a superimposed boundary correction unit 1 including a unit 16, a pattern memory 17, and a character recognition unit 18.
6 and the pattern memory 17 constitute a character cutout device.

The same functional blocks as those of the conventional OCR 5 shown in FIG. 5 are denoted by the same reference numerals. The program is usually stored in an internal storage device or an external storage device of the computer device, and is read and executed as needed. However, a recording medium separable from the computer device, for example, a CD-ROM And FD
Or the like, read by a computer device at the time of use, installed in the internal storage device or the external storage device, and provided for execution at any time.

The circumscribed rectangle integrating unit 13 is a circumscribed rectangle extracting unit 1
With respect to a plurality of character circumscribed rectangles from No. 2, respective start point coordinates and end point coordinates are added, and each character circumscribed rectangle and its coordinate information are input to the superimposed boundary detection unit 15. This is different from the circumscribed rectangle integration unit 13A of the conventional OCR 5 in which each character circumscribed rectangle is input to the pattern extraction unit 14.

The superimposition boundary detection unit 15 detects the presence or absence of superimposition between a plurality of input character circumscribed rectangles, and adds a superimposition flag to each of the character circumscribed rectangles. When the superimposition is detected, the size of the circumscribed rectangle outside the character, specifically, the start point coordinates or the end point coordinates is changed so as to avoid the superposition, and the superimposition flag is turned on. On the other hand, if no superimposition is detected, the superimposition flag is turned off. After adding the above information for all circumscribed rectangles,
The coordinate information of the circumscribed rectangle with the superimposition flag turned on and the superimposition flag are input to the superimposition boundary correction unit 16. When all the superimposition presence / absence flags are off, the coordinate information of each character circumscribed rectangle is input to the pattern extraction unit 14 sequentially from the top.

The superimposition boundary correction section 16 includes a superposition boundary detection section 1
Correction of the coordinate information of the character circumscribed rectangle input from 5 is performed. Specifically, the superimposition boundary is set based on the coordinate information of the character circumscribed rectangle whose superimposition presence / absence flag is on and the adjacent character circumscribed rectangle. In addition, all the line segment circumscribed rectangles existing in the region between the adjacent superimposed boundaries are acquired from the circumscribed rectangle extraction unit 12, and the character circumscribed rectangle to which each of these line segment circumscribed rectangles belongs is specified. If the character circumscribed rectangle can be specified, the coordinate information of each line circumscribed rectangle is further added to the coordinate information of the corresponding character circumscribed rectangle, and the line segment circumscribed rectangle in the image memory 11 is classified.

Here, the processing contents of the superimposed boundary detector 15 and the superimposed boundary corrector 16 will be described more specifically. For convenience, “East”, “Kyoto”, “Tokyo” as in FIG.
Will be described with an example of three character circumscribed rectangles arranged in this order.

First, the superimposition boundary detecting section 15 detects the presence or absence of superimposition of the two based on the coordinate information of the character circumscribed rectangle of the first "east" and the second character circumscribed rectangle of "Kyo". That is, the end point coordinates “X2” of “East” shown in FIG.
The start point coordinate “X3” of “K” is compared. If the difference between the two is greater than a preset overlap detection threshold value P1, it is determined that there is a overlap, and whether “East” and “K” are overlapped Turn on the flag. Similarly, based on the coordinate information "X4" and "X5" of the second character circumscribed rectangle of "K" and the third character circumscribed rectangle of "To", the presence or absence of superposition of both is detected. If the difference between the two is greater than a preset superimposition detection threshold value P1, the superimposition presence / absence flag for "city" is turned on.

The superimposition boundary correction section 16 corrects the coordinate information of each character circumscribed rectangle as follows. First, the size of the character circumscribed rectangle in which the superimposition flag added to each character circumscribed rectangle is on is corrected to a size that can avoid superimposition with an adjacent character circumscribed rectangle. That is, in this example, since the superimposition presence / absence flags of all the character circumscribed rectangles are turned on, the coordinates of the end point “X2” of “East” are set to coordinates “X21 (<X3)” for avoiding superimposition with “K”. , The starting point coordinate “X3” of “K” to the coordinate “X31 (>
X2)), the coordinates "X41 (<X4)" for avoiding the superimposition of "K4" with the end point coordinate "X4" of "Kyo" and the superimposition of the coordinates "X5" of the start point of "Kyoto" with "Kyo" are avoided. Coordinates “X51
(> X5) ".

The correction of the coordinate information is performed using a predetermined selection margin value. FIG. 3 is a schematic diagram showing this correction principle, in which two character circumscribed rectangles “East” and “K”
FIG. In FIG. 3, "X
“L” and “XR” are the coordinates of the superimposed boundary of the circumscribed rectangles of the characters “East” and “K.” The selection margin value is a value P determined according to the type of the document to be cut out.
2, the coordinate XL of the superimposed boundary for “East” is “X2-P2”, and the coordinate XR of the superimposed boundary for “K” is
Can be obtained by “X3 + P2”. This process is similarly performed for “K” and “To” to correct each coordinate information.

The superimposed boundary correction section 16 also obtains from the circumscribed rectangle extracting section 12 all the line segment circumscribed rectangles existing in the area between the superimposed boundaries (overlap boundary area), and each of these line segment circumscribed rectangles belongs. Specifies the character circumscribed rectangle. In the example of FIG. 3, two line segment circumscribed rectangles exist in the overlapping boundary region between “East” and “K”, but since the starting point coordinates of the line segment circumscribed rectangle in the upper part of the drawing coincide with the superimposed boundary XL, This is classified as belonging to the character circumscribed rectangle of "East". Then, the start point coordinates (Xa, Ya) and the end point coordinates (X
b, Yb) is added to the coordinate information of the circumscribed rectangle of the character “East”. Further, the line segment circumscribed rectangle shown in the lower part of the figure is classified as belonging to the character circumscribed rectangle of "K" because the start point coordinates do not coincide with the superimposed boundary XL, but the end point coordinates coincide with the other superimposed boundary XR. Then, the start point coordinates (Xc, Yc) and the end point coordinates (Xd, Yd) of the line segment circumscribed rectangle are added to the coordinate information of the character circumscribed rectangle of “K”. This process is called “Kyo”
The same applies to the overlapping boundary area between and "city".

FIG. 4 shows an example of various types of information added to each character circumscribed rectangle. In FIG. 4, "f1", "f
2 ”and“ f3 ”are superimposition presence / absence flags, and the line segment circumscribed rectangles (1), (2), and
The coordinate information corresponding to (3) and (4) is (X
a, Ya, Xb, Yb), (Xc, Yc, Xd, Y
d), (Xe, Ye, Xf, Yf), (Xg, Yg, X
h, Yh). The pattern extraction unit 14 extracts a character pattern in an area corresponding to each piece of coordinate information from the form image on the image memory 11 and stores the character pattern in the pattern memory 17. The character recognition unit 18 performs character recognition of the character pattern in the pattern memory 17 and outputs a recognition result to an output unit (not shown).

As described above, in the OCR 1 of the present embodiment,
When the superposition of the character circumscribed rectangle is detected between the character circumscribed rectangles, the coordinate information of the line segment circumscribed rectangle is added to the corresponding character circumscribed rectangle and output to the pattern extraction unit 14, so that the pattern extraction unit 14 Thus, an optimal character pattern cut-out area excluding the invading line segment can be immediately specified. Therefore, the process of tracing and whitening the character line boundaries as in the conventional OCR 5 is not required, and even a form or the like in which superimposition between characters is likely to occur can quickly extract a character pattern.

Further, when the superposition of the character circumscribed rectangle is not detected, the character recognition can be immediately started without performing the above-mentioned correction processing, so that the entire reading processing can be speeded up and the practicality in OCR is greatly improved. improves.

In the description of the present embodiment, it is assumed that the form image is a horizontally written character. However, the present invention is not limited to the above-described embodiment.
The same applies to vertically written characters. In this case, the above-described superimposition boundary or the like focusing on the X coordinate axis is expressed by:
It can be easily realized by appropriately setting the Y coordinate axis.

[0032]

As is clear from the above description, according to the character extracting apparatus of the present invention, the character pattern used for character recognition can be specified accurately and quickly. Further, according to the optical character reading device of the present invention, the time required for the recognition process can be significantly reduced while maintaining the character recognition accuracy at a certain value or more.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an optical character reading device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of coordinate information added to each character circumscribed rectangle according to the embodiment;

FIG. 3 is a diagram illustrating a superimposed boundary and an extra line segment circumscribed rectangle existing in the superimposed boundary region.

FIG. 4 is an explanatory diagram of coordinate information added to each character circumscribed rectangle by the processing of the embodiment.

FIG. 5 is a functional block diagram of a conventional optical character reader.

FIG. 6 is an explanatory diagram showing an example of a form image.

FIGS. 7A and 7B are diagrams illustrating a criterion for integrating line circumscribed rectangles, and FIG. 7B illustrates a primary circumscribed rectangle after integration.

FIG. 8 is an explanatory diagram of coordinate information added to a character circumscribed rectangle;

FIGS. 9A, 9B, and 9C are examples of character patterns cut out by circumscribed rectangles;

FIG. 10A is an explanatory diagram showing a conventional process of removing an intruding line, and FIG. 10B is an explanatory diagram of a character circumscribed rectangle from which an intruding line is removed.

[Explanation of symbols]

 1,5 Optical character reader (OCR) 11 Image memory 12 Bounding rectangle extracting unit 13,13A Bounding rectangle integrating unit 14 Pattern extracting unit 15 Superimposed boundary detecting unit 16 Superimposing boundary correcting unit 17 Pattern memory 18 Character recognizing unit

Claims (5)

[Claims] 1. A line segment circumscribed rectangle is extracted from an image including a plurality of character patterns, and the extracted line segment circumscribed rectangle is defined as a first line segment circumscribed rectangle.
Direction, and the circumscribed rectangle of the line
A character circumscribed rectangle creating means for dividing a plurality of character circumscribed rectangles in a second direction perpendicular to the direction, and a coordinate of one end point and a start point coordinate of the other of the pair of character circumscribed rectangles adjacent in the second direction. Superimposition detection means for determining whether the difference is equal to or greater than a predetermined superimposition detection threshold, and designating a character cut-out area of a size corresponding to the determination result; and a corresponding character pattern from the image image based on output information of the superimposition detection means. And a character extracting device for extracting a character. 2. The superimposition detecting means, when the difference is less than the superimposition detection threshold, designates coordinate information of an individual character circumscribed rectangle as the character cutout area, while the difference is greater than or equal to the superimposition detection threshold. In the case of, each character circumscribed rectangle is changed to a size that avoids overlapping with another character circumscribed rectangle, and coordinate information of the line circumscribed rectangle existing in the difference area and the character circumscribed rectangle to which the line circumscribed rectangle belongs 2. The character segmenting device according to claim 1, wherein the coordinate information is designated as the character segmenting region. 3. The character clipping device according to claim 2, wherein the difference area is automatically set based on a predetermined margin value. 4. An image memory for storing an image including a plurality of character components read by an optical scanning means, and extracting a plurality of line segment circumscribed rectangles from the image stored in the image memory. A character circumscribed rectangle creating means for integrating the plurality of line segment circumscribed rectangles in a first direction and dividing the combined line segment circumscribed rectangle in a second direction perpendicular to the first direction to create a plurality of character circumscribed rectangles; It is determined whether a difference between one end point coordinate of the pair of character circumscribed rectangles adjacent in the second direction and the other start point coordinate is equal to or greater than a predetermined superimposition detection threshold value, and a character cutout area having a size according to the determination result is determined. Superimposition detection means to be designated; pattern extraction means for extracting a corresponding character pattern from the image based on output information of the superimposition detection means; and a sentence based on the extracted character pattern. Optical character reading apparatus comprising and a character recognition means for recognizing. 5. A process for extracting a line segment circumscribed rectangle from an image including a plurality of character patterns, integrating the extracted line segment circumscribed rectangle in a first direction,
A process of dividing the integrated line segment circumscribed rectangle in a second direction perpendicular to the first direction to create a plurality of character circumscribed rectangles; one end coordinate of a pair of character circumscribed rectangles adjacent in the second direction and the other The process of determining whether the difference from the start point coordinates is equal to or greater than a predetermined superimposition detection threshold.If the difference is less than the superimposition detection threshold, the coordinate information of each character circumscribed rectangle is specified as a character cutout area. If the difference is equal to or greater than the superimposition detection threshold,
The size of each character circumscribed rectangle is changed to a size that avoids overlapping with other character circumscribed rectangles, and the coordinate information of the line circumscribed rectangle existing in the difference area and the coordinate information of the character circumscribed rectangle to which the line circumscribed rectangle should belong A computer-readable recording medium storing a program for causing a computer to execute a process of designating a character extraction region as a character extraction region, and a process of extracting a corresponding character pattern from the image image based on the designated coordinate information.