JPS603677B2 - Stroke end point extraction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for extracting end points of strokes that constitute figures such as letters and numbers.

Stroke endpoints, like intersections and loops, are important features of characters. In the conventional stroke end point extraction method, a figure is thinned using, for example, a 3×3 mask, and stroke end points are extracted based on the thinned figure. The conventional stroke end point extraction method described above has drawbacks such as requiring a very large number of processing steps and large tables to perform the thinning process. The present invention aims to eliminate the above-mentioned drawbacks, and provides a stroke end point extraction method that does not require tables, is short, and can extract the end points of a stroke in a processing step. The purpose is Therefore, the stroke end point extraction method of the present invention scans the entire character frame surrounding the character with scanning lines in a predetermined direction, and detects the end points of the stroke using the scanning information obtained in this way. Change point detection means for detecting the first change point from white to black and the last change point from black to white based on the scanning information each time a line is scanned, and two changes in adjacent scan lines. A discontinuous part detection means for detecting a discontinuous part in a point series composed of a plurality of changing points by checking whether the distance between the points exceeds a predetermined value, The stroke end point is characterized by checking whether the segment is shorter than a predetermined value and protruding from the segments on both sides, and setting the coordinates representing the segment that is shorter and protruding than the predetermined value as the coordinates of the stroke end point. It is.
Hereinafter, the present invention will be explained with reference to the drawings. FIG. 1 is a diagram for explaining the stroke end point extraction principle used in the present invention, FIG. 2 is a diagram showing an image signal, its rising and falling edges, and a scan gate signal, and FIG. 3 is a diagram showing one implementation of the present invention. An example block diagram, FIG. 4, is a diagram showing the storage format of the start point, end point, and contents of the continuous counter.

In FIG. 1, S to Mi are the start points of the segments forming the upper contour line, E to E5 are the end points of the segments forming the upper contour line, S',
S to S'3 are the start points of the segments forming the lower contour, E' to E'5 are the end points of the segments forming the lower contour, and 0 is a flag.

The principle of stroke end point extraction used in the present invention will be explained with reference to FIGS. 1 and 2.

In FIG. 2, the period when the scan gate is "1" corresponds to the height of the character frame. Also,
An image signal of logic "1" corresponds to black, and an image signal of logic "0" corresponds to white. Figure 2A is for scanning line Xs, and Figure 2A is for scanning line Xs2. When the scanning line comes to row Xs, the image signal rises from "0" to "1" at point S, and from "1" to "1" at point S'.
0". In this case, point S, is the first point of change from white to black, and point S', is the last point of change from black to white. Xs. Since there is no black in the -1 line, points S and S' become starting points. The coordinates of the starting point S, are expressed as (Xs,, Ys,),
The coordinates of the starting point S', are (Xs,, Ys',)
It is expressed as When the scan line reaches the (Xs, 11) row, the first transition point from white to black and the last transition point from black to white are similarly detected. The Y coordinate of the above two change points is Y
Assume that s, 11 and Ys', 11. Xs,
Find the difference between the Y coordinates Ys, and Ys,11 of the first change point from white to black in the row, and if this difference is less than a predetermined value, for example 3, the point series of the change points at Xs is continuous. Define that there is. A similar definition applies to the series of points consisting of the final change from stupid to white. The scanning line is Xs
When the time limit is reached, an image signal with rising and falling edges as shown at the beginning of Figure 2 is obtained.

Let Ys2 be the Y coordinate of the first point of change from white to black in the Xs2 row, and Ys'2 be the point of change from white to white. X
Let Ye be the Y coordinate of the first point of change from white to black in line s2-1, and find the difference between Ys and Ye. If this difference is greater than a predetermined value, for example "3", the point series consisting of the first change point from white to black becomes discontinuous at Xs2. Point S2 becomes the starting point, and point E,
is the end point. In a point series consisting of the first change point from white to black, if the direction from the start point to the end point is opposite to the scanning line direction, the flag "0" is attached to the end point, and the direction from the start point to the end point is If the direction toward is equal to the scanning line direction, a flag "0" is attached to the start point. In the point series consisting of the last point of change from black to white, the flag "○" is attached in the opposite way to the above. Thus, when the entire character frame is scanned with a scanning line in the Y direction, an upper contour line and a lower contour line are obtained which are composed of a plurality of segments defined by the start point and the end point. By the way, when writing characters with a writing instrument, the width of the stroke of the character is determined by the writing instrument.

Therefore, in order to find the end point of a character's stroke, it is necessary to make sure that the length of the 'E' segment is less than or equal to a predetermined length among the multiple segments that make up the outline, and that the start and end points of the 'Low' segment are flagged. All you have to do is find a segment that satisfies the following two conditions: no tags are attached.

The above predetermined length is, for example, 9 mesh width. Assuming that the segments S383 and S'2E'2 are shorter than 9 meshes, their midpoints are respectively the end points of the stroke. FIG. 3 shows one embodiment of the present invention.

In the figure, 1 is a scan counter, 2 is a rising detection circuit, 3 is a falling detection circuit, 4 and 5 are registers, 6-1 and 6-2 are scan registers, and 7-1 and 7-2 are also A scan register, 8 and 9 are arithmetic circuits, and 10 and 11 are continuous counters, respectively. The scan counter can be thought of as indicating the current scan line position. The rising edge detection circuit 2 detects the rising edge of the image signal from "0" to "1" and sends the rising position to the register 4. This rising position corresponds to the Y coordinate of the first change point from white to black in FIG. When the rising position is stored in register 4, a sample prohibition signal is output,
After that, input of the image signal to the rising edge detection circuit 2 is prohibited. The rising position of register 4 and the scanning line position of scan counter 1 are stored in register 6-2. The falling detection circuit 3 detects the image signal from “1” to “0”.
This detects the falling edge of the signal and stores the falling position in the register 5. The falling position of register 5 is written to register 7-2. Even if there are multiple falling edges while scanning one line, the contents of the registers 7-2 are rewritten one after another, so that the last rising position is saved as valid. Note that the contents of the register 6-2 are transferred to the register 6-1 when the scan gate falls from "1" to "0". The same applies to register 7-1. Arithmetic circuit 8
The difference between the rising position of the register 6-1 and the rising position of the register 6-2 is determined. This difference is the predetermined value,
For example, if the value is "3" or less, a logic "1" is output, and the contents of the continuous counter 10 are thereby incremented by 11. When the difference between the rising position of register 6-1 and the rising position of register 6-2 is larger than a predetermined value, the coordinates of the end point are determined by the contents of register 6-1, and the coordinates of the end point are determined by the contents of register 6-1.
The coordinates of the start point are determined by the contents of 2.
A flag is then attached depending on the sign of the difference.
Also, at this time, the contents of the continuous counter 10 are read out, and after the discussion, the continuous counter 0 is cleared. The contents of the start point/end point and the continuous counter 10 are written to a start/end feature pair memory (not shown) in the formats shown in FIG. 4, respectively. Note that the segment number can be obtained by counting the number of discontinuities in the point series consisting of the first change point from white to black. Arithmetic circuit 9 and continuous counter 11 operate similarly to arithmetic circuit 8 and continuous counter 10. However, the calculation circuit 9 starts calculation after the scan gate falls from "1" to "0". Then, the start point, end point, and contents of the continuous counter 11 in the point series consisting of the last change point from black to white are written into the above start-end feature pair memory in the format shown in FIG. The end points of a stroke can be found by examining the start/end feature pair memory described above.As is clear from the above description, according to the present invention, the total points of a stroke are
It can be extracted with shorter processing steps and less hardware.

Although the above embodiment is an example of extracting the upward stroke end points and the total downward stroke points, it is also possible to similarly extract the leftward stroke end points and the total rightward stroke points by scanning the figure with a horizontal scanning line. will appear.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the stroke end point extraction principle used in the present invention, Fig. 2 is a diagram showing an image signal, its rise and fall, and a scan gate signal, and Fig. 3 is a diagram showing one implementation of the present invention. An example block diagram, FIG. 4, is a diagram showing the storage format of the start point, end point, and contents of the continuous counter. 1...Scan counter, 2...Rise detection circuit, 3...Fall detection circuit, 4 and 5
...Registers, 6-1 and 6-2, 7-1 and 7-2...Scan register, 8 and 9...Arithmetic circuit,
10 and 11... Continuous counter. spear 1 zusun 2 kyou (a) ryo z koku 〇) ryo 3 kyou 4 legs

Claims (1)

[Claims] 1 In a stroke end point detection method in which the entire character frame surrounding a character is scanned with a scanning line in a predetermined direction and the end point of a stroke is detected based on the scanning information thus obtained, the scanning information is collected every time one line is scanned. change point detection means for detecting the first change point from white to black and the last change point from black to white based on the two
The discontinuous part detection means detects a discontinuous part in a point series made up of a plurality of change points by checking whether the distance between two change points exceeds a predetermined value, It is characterized by checking whether the divided segment is shorter than a predetermined value and protruding from the segments on both sides, and setting the coordinates representing the segment that is shorter and protruding than the predetermined value as the coordinates of the stroke end point. Stroke end point extraction method.