JPH01201786A - Character reader - Google Patents

Abstract

PURPOSE:To precisely detect and segment respective characters so as to submit them for a recognition processing by obtaining the positions of the segment of the characters and the directions of segment from projection in plural directions. CONSTITUTION:A character detection segment part 2 detects and segments respective character pictures from character string pictures which a photoelectric conversion part 1 has image-picked up and inputted in accordance with detection segment information, and submits them for the character recognition processing by a character recognition part 3. Detection segment information can be obtained by obtaining the positions of the segment of the characters and the directions of segments from the projection in plural directions by a row direction segment part 4, a projection generation part 5 and a minimum projection detection part 6 and detecting the segments of respective characters.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a character reading device that can accurately recognize each character in a character string image read by a reading means.

(Prior art) Reading and recognition of characters in a character string image captured and inputted by a photoelectric conversion unit, which is a reading means, basically involves detecting and cutting out each character image from the character string image, and then Compare the character pattern by calculating the degree of similarity between the character pattern and the standard pattern of the character to be read registered in the dictionary in advance, obtain recognition candidates according to the verification result, and further specify the character indicated by the character image. carried out by.

However, in character reading devices that read and input handwritten characters, the size of each character in the handwritten character string is uneven, and the spacing between the characters varies, etc. The so-called reading detection process for cutting out individual character images from each character image has become extremely difficult. For this reason, various studies have been carried out on how to detect and cut out character images with high accuracy.

By the way, the above-mentioned detection and cutting process is normally performed on the premise that each character falls within a rectangular circumscribing frame. Specifically, this is performed by obtaining a projection of a character string image in a direction perpendicular to the character string direction, and detecting character break positions in the character string direction from this projection pattern. However, in handwritten character strings, especially Japanese texts written horizontally, the characters themselves are often written with an inclination, as in so-called cursive characters.

Moreover, the direction of the inclination is often not constant within a single character string. For this reason, combined with the uneven character spacing mentioned above, there were problems such as the detection and extraction process of each character image forming a character string becoming unnecessarily complicated and requiring a large amount of processing time. . Furthermore, since each character image cannot be detected and cut out with high precision, problems arise, such as that it is difficult to improve the reading accuracy.

(Problem to be Solved by the Invention) Conventionally, for example, when the orientation of each character of a handwritten character string is uneven, it is difficult to Detection and extraction processing of character images is difficult, and there have been problems such as not only being unable to improve detection and extraction accuracy, but also being unable to improve character reading accuracy due to this. .

The present invention has been made in consideration of these circumstances, and its purpose is to ensure that each character string that makes up the character string is not aligned even if the characters are in irregular orientations, such as those that include italic characters. It is an object of the present invention to provide a character reading device capable of detecting and cutting out character images of characters with high precision and improving character reading accuracy.

[Structure of the Invention] (Means for Solving the Problems) A character reading device according to the present invention detects the character string direction for a character string image forming a character string extracted from an image read and input by a reading means. Find the projections for a plurality of directions that intersect with each other, compare these projections with each other, and find the minimum projection value among the projections for each position in the character string direction,
From these minimum projection values and the minimum projection pattern indicated by the direction of the projection from which the minimum projection value was obtained, for example, the minimum projection pattern is binarized with a predetermined threshold value to separate each character in the character string image. The present invention is characterized in that the position is determined, and at the same time, the direction of character separation is determined from the direction of projection at that position, and detection and segmentation is performed in accordance with this information.

(Function) According to the present invention, even when reading and inputting a character string consisting of handwritten characters with irregular inclinations, the positions of character breaks and the directions of the breaks can be determined from projections in a plurality of directions. Since the breaks in each character are detected, each character image can be detected and cut out with high precision according to the information on the breaks and subjected to recognition processing. As a result, it becomes possible to read and input characters with high precision.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of the main parts of a character reading device according to an embodiment of the present invention, and FIG. 8 shows the flow of its overall processing procedure.

The photoelectric conversion unit l, which is the reading means, is composed of a TV camera, a semiconductor image sensor, etc., inputs the character string information written on the form as an image, and digitizes the character string image (process A in Fig. 8). . This digital image is temporarily stored in a frame memory, and is used for reading and inputting character information as described below.

The character detection and cutout unit 2 detects and cuts out individual character images from the input character string image as described above in accordance with detection and cutout information to be described later, and subjects them to character recognition processing by the character recognition unit 3.

The detection and extraction information used in the character detection and extraction process described above is obtained as follows.

The line detection/cutting unit 41 obtains the projection of the input image in the vertical and horizontal directions, respectively, and detects the region of the character string image (processes B and C in FIG. 8). The images of the individual character string image regions obtained by the line detection and cutout section 4 are each subjected to character detection and cutout processing.

The projection creation unit 5 calculates projections of the character string image obtained by the line detection and cutting unit 4 in a plurality of directions intersecting the direction of the character string. Specifically, for example, for a character string image cut out with a line width as shown in FIG. 2, a plurality of preset directions 1. II, the projection on ~V is the fourth
Each is calculated as shown in the figure (Processing D in Figure 8).
1. D2°~Dn). Note that here, one of the directions in which projection is sought, ■, is defined as a direction perpendicular to the character string direction. Directions I and II are used to detect breaks in so-called forward-slanted characters (left italic characters) in a horizontally written character string, and directions IV and V are used to detect breaks in so-called backward-slanted characters (right italic characters). Each direction is determined as a direction.

Then, the minimum projection detection unit 6 compares the projections obtained in each direction as described above at each position in the character string direction, and calculates the minimum projection among those projection values. The value and the above-mentioned projection direction information from which the projection value was obtained are obtained as a minimum projection pattern as shown in FIG. 5 (processes E1 and E2 in FIG. 8). That is, as shown in FIG. 5, the projection pattern α in which the minimum projection value was extracted at each position in the character string direction, and the projection direction β in which the minimum projection value was obtained at each position in the character string direction are determined. ing. In addition, in the minimum projection pattern shown in FIG. 5 obtained from the projections in a plurality of directions shown in FIG. It is shown that Such processing is repeated for all bits in the character line direction (processing F in Figure 8).
.

The minimum projection detection unit 6 performs a binary evaluation of the minimum projection pattern a obtained in this manner using a predetermined threshold value (processing G in FIG. 8), and estimates its character pitch (processing H in FIG. 8).

Then, as shown in Fig. 6, the character break position is determined (process 1 in Fig. 8), and at the same time, the direction of the character break at that break position is determined in the projection direction that obtained the minimum projection value of the minimum projection pattern described above. It is obtained from β (processing J in Figure 8). Such a character break detection process is repeatedly executed for all characters (process K in FIG. 8).

The information on the position of the characters detected as shown in FIG. 6 and the information on the orientation of the characters are used together with the detection information on the character string area as the above-mentioned detection extraction information by the character detection and extraction unit 2. given to.

For example, when an input character string image is given as shown in FIG. 2, the character detection and extraction section 2 calculates the separation position of each character as shown in FIG. For each character image, detection and extraction processing is executed according to the direction of character separation, and each character image is detected and extracted.

Note that the detected and cropped character image is subjected to normalization processing for the orientation of the character as appropriate according to the information on the direction of extraction, etc., and then subjected to character recognition processing (see Fig. 8). Processing, M). Then, the character recognition process is performed by calculating the degree of similarity between the detected and extracted character image and the dictionary pattern as described above, and, for example, finding the dictionary pattern with the maximum degree of similarity as the recognition result (see Fig. 8). processing N).

The recognition result obtained in this way is output as the character reading result of the input image (process O in FIG. 8).

Thus, according to this device equipped with such a character detection and extraction processing function, even if the character string to be read and input includes handwritten cursive characters with irregular orientations, part of the character pattern is Each character can be detected and cut out with high precision without causing defects such as missing parts or parts of adjacent character patterns entering, so each character can be read and recognized with high precision. It becomes possible to input. As a result, it is possible to significantly reduce erroneously detected extraction of character images and improve the reading accuracy.

Note that the present invention is not limited to the embodiments described above. Here, projections in five directions are obtained. However, the setting of the direction and the number of settings may be determined depending on the nature of the character to be read. In addition, although the description has been made using an example of character image detection processing for horizontally written character strings, the present invention is similarly applicable to vertically written character strings. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a schematic diagram of the main parts of a character reading device according to the embodiment, and Fig. 2 is a diagram showing an example of a character string image obtained by line detection. Figure 3 is a diagram showing an example of the direction in which to obtain the projection for a character string image.
Figure 5 shows an example of the minimum projection pattern obtained from the projection shown in Figure 4. Figure 6 shows the projection of the character string image in multiple directions. FIG. 7 is a diagram schematically showing character detection and extraction processing according to the detection and extraction information shown in FIG. 6. FIG. 8 is an example of the processing procedure in the embodiment device. FIG. l...Photoelectric conversion unit, 2...Character detection cutting unit, 3...
-Character recognition unit, 4... Line detection cutting unit, 5... Projection creation unit, B... Minimum projection detection unit. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Av > f (III) Figure 7

Claims (1)

[Claims] a character string detection unit that detects a character string image area forming a character string from an image read by the reading means; and a projection of the character string image obtained by the character string detection unit in a plurality of directions intersecting the character string direction. and the minimum projection value in the projections obtained for each of the plurality of directions for each position in the character string direction, and in the direction of the projection in which these minimum projection values and the minimum projection value were obtained. and means for detecting and cutting out individual character images from the character string image by determining the position and direction of character separation from the minimum projection pattern. Character reading device.