JPH0243220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to character recognition, and more particularly to a character feature extraction method.

Character recognition is performed by identifying characters having the characteristics based on information obtained by various character feature extraction methods. At this time, various means have been conventionally employed as a method for extracting the characteristics of characters, and in order to accurately recognize characters, many types of means are required.

In view of the above points, the present invention is characterized by providing a novel feature extraction method for extracting character features.

The feature extraction method of the present invention includes means for inputting a character pattern, and scanning lines are sequentially moved toward the character pattern in a plurality of directions with respect to the area of the input character pattern until the character pattern is detected. a circumscribed polygon generating means for calculating a circumscribed polygon of the character pattern whose sides are the scanning lines when the pattern is detected; a barycenter position detecting means for determining the barycenter position of the input character pattern; A distance generation circuit that creates a distance drawing centered on the obtained center of gravity position, and a distance generation circuit that calculates the position of a point where a line radiating from the center of gravity of the character pattern in multiple directions intersects the circumscribed polygon, and calculates the distance drawing from the distance drawing. This feature extraction method is characterized by comprising a measuring means for measuring the distance from the center of gravity, and detecting the features of the character pattern from the distance.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The feature extraction method of the present invention shown in FIG. 1 includes a circumscribed polygon generation circuit 1 to which character input is applied, a barycenter position detection circuit 2-1 to which character input is applied, and a distance generation circuit 2-2. Distance image creation circuit 2
The basic configuration includes a feature generation circuit 3 to which the outputs of a circumscribed polygon generation circuit 1 and a distance image generation circuit 2 are input.

For example, the input character "ei" as shown in FIG. 2a, which is applied to the character input terminal _T1 , is input as shown in FIG. It is processed to generate its circumscribed polygon 10 as shown. In other words, the address space is rectangular area 1
It is treated as 1 and the input character “ei” is inputted into the area 11 as the second character.
Store it as a data pattern as shown in figure a,
Scanning starts from a plurality of points 10 ₁ to 10 _k along the sides of the address space rectangular area 11 and scans in a pre-specified direction from point 10 ₁ to 10 _k sequentially inside the rectangular area 11. Select and scan to move. The lines scanned from each starting point are parallel to each other, and the scanning line _11k where the input character "ei" is first detected is defined as one side of the circumscribed polygon 10. Thereafter, similar processing is performed a predetermined number of times, thereby repeating the same number of times as the number of sides of the circumscribed polygon. Each line that has detected “eong” obtained through the above-mentioned motion processing is a circumscribed polygon 10
generate. Incidentally, when the scanning line is in the x direction or the y direction, the input character "ei" can be accessed by using the output of the counter as an address. In the case of access using diagonal scanning lines as illustrated in Fig. 2a, since the address to be accessed changes regularly when focusing on a certain scanning line, the start address, address displacement direction, and end address are stored in memory in advance. If you do this, you can generate an access address relatively easily.

Next, any one in the rectangular area 11 of the address space
For example, find the center of gravity 0 of the input character "ei" as a point, and calculate the distances d ₁ from this center of gravity 0 to multiple points on the sides of the circumscribed polygon 10, as shown in Figure 3a.
Measure d ₁₂ . The x-coordinate of the center of gravity 0 of the character “ei” is
It is obtained by taking the sum of the x-coordinates of pixels and dividing by the number of pixels. Similarly, the y-coordinate of the center of gravity 0 can also be determined.

Center of gravity position detection circuit 2-1 in distance image creation circuit 2
is a circuit that calculates the position of the center of gravity, which temporarily stores the input character ``English'' (character image), sequentially adds the X and Y coordinates where dots exist, calculates the number of dots, and calculates the X coordinate when all dots are counted. and Y
Divide the coordinate addition result by the coefficient result and use the result as the center of gravity position.

The distance A is measured by the distance generation circuit 2-2 of the distance image creation circuit 2 shown in FIG. 1 using the 3.times.3 window processing circuit 20 shown in FIG. 3b. As shown in FIG. 3b, this window processing circuit 20 has three stages of shift registers 21 connected in series, each having a number of cells equal to the number of cells (unit area) in the x-axis direction of the address space rectangular area 11. Pixel data from the spatial rectangular area 11 is transferred to the shift register 2.
Enter 1. 3 of the 3 stage shift registers
The window 22 is formed using x3 cells.

In advance, the flag bit of the center of gravity 0 is set to 1, and the flag bits of the other points are set to 0. This flag bit is input to the shift register.

First, scan the window (move across the entire screen), and if the cell at the center A is 0 and at least one of the surrounding 8 points is 1, define the pixel corresponding to A as 1, and at the same time set the flag bit to 1. . This defines the eight 1's in FIG. 3c.

Next, scan the window again, define point 2 using similar logic, and set the flag bit to 1.

Thereafter, by repeating the window scan a total of n times in the same manner, a distance image consisting of pixels defined as 1 to n as shown in FIG. 3c is obtained. Next, the feature generation circuit 3 generates a circumscribed polygon 1 in the distance picture.
The number defined for the pixel corresponding to the 0 side, for example l
From this, the distance dl from the center of gravity 0 to the circumscribed polygon 10 is obtained. By measuring a plurality of distances d from the center of gravity 0 to a plurality of points of the circumscribed polygon 10, the characteristics of the input character "ei" are obtained as a string of distances as shown in FIG. Extract the features of the input character ``ei'' using .

As described above, according to the present invention, a circumscribed polygon is generated in a rectangular area of an address space for an input character, and a plurality of distance information from an arbitrary point to a plurality of points on a side of the circumscribed polygon is generated. This method measures character characteristics and extracts character features.This feature extraction method allows for more accurate character recognition.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of the feature extraction method of the present invention, FIG. Similarly, an image diagram of an input character and a circumscribed polygon is shown. Figure 3a is a diagram showing the distance between a side of a circumscribed polygon and an arbitrary point in a rectangular address space area. Figure 3b is a block diagram of a 3x3 window processing circuit. 3c is a distance image formed by the window processing circuit, and FIG. 3d is a distance image formed by a plurality of distances shown in FIG. 3a. 1... Circumscribed polygon generation circuit, 2... Distance image generation circuit, 3... Feature generation circuit, 10... Circumscribed polygon, 11 ₁ to 11 _k ... Scanning line, 11... Address space rectangular area, 21 ...Shift register, 22...
...3x3 window processing circuit.

Claims (1)

[Scope of Claims] 1. means for inputting a character pattern; a means for inputting a character pattern; a circumscribed polygon generating means for calculating a circumscribed polygon of the character pattern whose sides are scanning lines when the pattern is detected; a center of gravity position detection means for determining the position of the center of gravity of the input character pattern; a distance generating circuit that creates a distance drawing centered on the obtained center of gravity; a distance generation circuit that calculates the position of a point where a line radiating in multiple directions from the center of gravity of the character pattern intersects the circumscribed polygon; A feature extraction method comprising a measuring means for measuring a distance from a center of gravity, and detecting features of a character pattern from the distance.