JP2658153B2 - Character identification method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character identification method for identifying a character based on features of a line segment of a contour forming a pattern of a read character.

(Prior Art) Conventionally, as character identification methods for identifying characters including alphanumeric characters and katakana, a stroke analysis method for analyzing a stroke of a character, a pattern matching method for checking a match between a character pattern and a reference pattern, and further, Various methods have been proposed as methods for dealing with deformed characters, such as a method for analyzing the line structure of a character pattern and a method for analyzing the background structure.

Further, Japanese Patent Application No. 58-34482 filed by the present applicant discloses a technique of storing a start point and an end point of a line segment forming a stroke of a character to be identified, and identifying the character based on the distribution position of the line segment. It has been disclosed.

(Problems to be Solved by the Invention) However, the stroke analysis method must have a dictionary for identifying characters, which describes the characteristics of each character including deformed characters, and therefore the amount of information is enormous. And there is a disadvantage that the processing time becomes longer. In order to shorten such processing time, there is a disadvantage that the scale of hardware must be increased.

Also, the method of analyzing the background structure focuses on the background portion of the described character, extracts loops, concave states and convex states of lines forming the character as its features, and based on this feature, This executes a process for recognizing characters. This process requires a process of determining a black and white point of an image forming a character in order to identify a character line. However, such a process generally has a disadvantage that it is complicated.

In the character identification system of Japanese Patent Application No. 58-34482 filed by the present applicant, the start point and the end point of a line segment of a stroke forming a character to be identified must be stored. However, there was a drawback that it became complicated.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a character identification system in which identification processing is simple, and therefore, high-speed and accurate.

(Means for Solving the Problems) The present invention extracts a character outline from a binarized character pattern of a character to be identified, and identifies the character from a plurality of feature points related to the outline. It relates to an identification method. According to the invention, in particular, the xy
From the contour information representing the coordinate position, the characteristic value indicating the distribution position of each contour line forming the contour is defined as x of x component of each contour line in a relative coordinate system with respect to a predetermined reference position.
Position on the axis, position on the y axis of the x component of each contour line, position on the y axis of the y component of each contour line, and position on the x axis of the y component of each contour line A feature value calculating means for calculating a feature value related to the feature value, and a comparison between the feature value calculated by the feature value calculating means and a reference feature value predetermined for each of a plurality of characters. And an identification means for identifying a character corresponding to the feature amount from a character of the character pattern when a difference between the two indicates a minimum value.

(Operation) The feature quantity indicating the distribution position of the contour line is
From the contour information representing the xy coordinate position, the position on the x axis of the x component of each contour line in the relative coordinate system with respect to a predetermined reference position, the position on the y axis of the x component of each contour line, The position of the y component of the contour on the y-axis, and the y of each contour
It is obtained as a feature value relating to the position of the component on the x-axis.
The difference between this feature and the predetermined reference feature amount is minimized when both are the same. Therefore, the identification means extracts the reference feature amount indicating the smallest difference, and determines that the corresponding character is the character to be identified, thereby performing a process for identifying the character. Be simple and accurate.

(Example) An example will be described with reference to the drawings. Figure 1
FIG. 1 is a block diagram of a character identification system showing one embodiment of the present invention. In FIG. 1, 1 is a binarized character pattern.
A pattern register 2 for storing the outline 1a of the character pattern 1b from the character pattern 1b output from the pattern register 1 by a known method.
Is a feature amount calculation unit that calculates a feature amount 3a indicating a distribution position of a contour line segment of the character pattern 1b described below from the outline 2a extracted by the outline extraction unit 2, 4 is an identification unit, and 4 is an identification unit. 3 is compared with a predetermined reference feature amount, and when it is detected that the difference between the two is minimized, the character corresponding to the reference feature amount is determined. It is determined that the character is the character of the character pattern 1a, and the result 4a of this determination is output.

Next, the operation of such a configuration will be described. A known character pattern input unit (not shown) reads a character (not shown) to be identified, for example, a character "A" on a book. Then, as shown in FIG. 2, a character pattern 1a composed of binarized data is output in association with the position of the xy coordinate. The pattern register 1 inputs and stores such a character pattern 1a and outputs it as a character pattern 1b.

In order to track the outline of the character pattern 1b output from the pattern register 1, the outline extraction unit 2 uses, for example, the xy coordinates of the xy coordinate located at the upper end of the character "A" as shown in FIG. Take (9,32) and (11,24)
The contour tracking is started with these as starting points. Thereby, as shown in FIG. 3, the outline of the character pattern 1b is
A series of contour information representing the xy coordinate position is extracted as a contour 2a. In this case, the starting point can be arbitrarily selected. The extraction method for extracting such contour information may be a known method and is not the object of the present invention, and therefore, a detailed description is omitted here.

First, the feature quantity calculation unit 3 inputs the contour 2a, and quantifies where each line segment on the contour 2a is located on the xy coordinate for each of the x component and the y component of the line segment. After that, while having their respective average values, the feature quantity Q ₁ related to the position of the x component on the x axis, the feature quantity Q ₂ related to the position of the y component on the y axis, the y axis of the x component Features related to the upper position
Q ₃ and a feature quantity Q ₄ related to the position of the y component on the x-axis are calculated as follows. However, H _x, H _y represents a character width of a character pattern 1a, x _i, y _i is the position on the xy coordinate.

Here, when shown on the xy coordinates in FIG. 3, the feature amounts Q _{1 to} Q ₄ are relative positions in a coordinate system having the origin at (1,1) which is the lower left position of the rectangle circumscribing the character pattern 1a. It should be noted that the calculation is based on Therefore, the feature quantities Q _{1 to} Q ₄
Is smaller as the line segment is closer to the origin. Further, since the feature amounts Q _{1 to} Q ₄ include a term obtained by adding all the line segments related to the position on the xy coordinate, the change of the line segment is the feature amount Q ₁
Impact on to Q ₄ is smaller than the segment changes in the position close to the origin, larger line segment changes in the position close to the upper right of the rectangle circumscribing the character pattern 1a.

Since the feature quantities Q _{1 to} Q ₄ have such a property, in the present invention, in order to facilitate the identification of characters, the upper right coordinate position (22, 32) of the rectangle circumscribing the character pattern 1a is further set as the origin. and obtains the contour 2a that, they feature quantity Q ₅ to Q ₈ are applied to a computing equation that derives the characteristic amount Q ₁ to Q ₄ may be derived.

Further, the feature quantity Q ₁ in the outer edge contour shown in FIG.
And to Q _8, the feature quantity Q ₁ in the inner edge contour shown in FIG. 4 (b)
By obtaining the sum of the to Q _8, calculates a characteristic quantity Q ₁ to Q ₈ character pattern 1a derived from the contour 2a. When a plurality of inner edges exist in a character to be identified, the above operation is performed on all the line segments.

The identification unit 4 stores reference feature amounts of characters included in the identification target range. These reference features and
By comparing the feature quantity Q ₁ to Q ₈ character pattern 1a derived from the contour 2a sequentially difference between them, i.e. to derive a matching distance. From the derived matching distances, a reference feature indicating the minimum value is selected by sorting. The identification unit 4 determines that the character corresponding to the reference feature amount selected in this way is a character to be identified, and outputs this as a result a.

(Effects of the Invention) According to the present invention, as described in detail above, according to the present invention, based on contour information representing an xy coordinate position of a contour,
As a feature indicating the distribution position of each contour line forming the contour, the position on the x-axis of the x component of each contour line in a relative coordinate system with respect to a predetermined reference position, A feature value is calculated for the position on the y-axis, the position of the y component of each contour line on the x-axis, and the position of the y component of each contour line on the x-axis. Therefore, character identification processing is very simple and fast, and the reliability of the identification result is high.

[Brief description of the drawings]

FIG. 1 is a block diagram of a character identification system showing an embodiment of the present invention, FIG. 2 is a pattern diagram of a character to be identified, FIG. 3 is a diagram showing the outline of the character in FIG. 2, and FIG. FIG. 3 is a diagram of a coordinate series of the outline of the character in FIG. 2; 3 ... Feature point extraction unit, 4 ... Identification unit.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-290985 (JP, A) JP-A-62-269286 (JP, A) IEICE Technical Report PRL82-29 IEICE Technical Report PRL82 − 79

Claims (1)

(57) [Claims] 1. A character identification method for extracting an outline of a character from a binarized character pattern of a character to be identified and identifying the character from a plurality of feature points related to the outline. From the contour information representing the xy coordinate position of
As a feature amount indicating a distribution position of each contour line forming the contour, a position on the x axis of the x component of each contour line in a relative coordinate system with respect to a predetermined reference position, an x component of each contour line A feature amount calculating means for calculating a feature amount related to a position on the y-axis, a position on the y-axis of a y component of each contour line, and a position on the x-axis of a y component of each contour line; The feature amount calculated by the feature amount calculation means is compared with a predetermined reference feature amount corresponding to each of a plurality of characters, and when a difference between the two shows a minimum value. A character identification method comprising: identification means for identifying a character corresponding to the characteristic amount from a character of the character pattern.