JPH06231240A - Method for approximating outline - Google Patents

Abstract

PURPOSE:To easily transform image data into vector data by finding out coincidence between a straight line connecting one of two extracted points on the outline of the image data to a newly extracted point and the outline. CONSTITUTION:A point E with a maximum interval (tm1) between a segment AB and the AB component of an outline CL is stored as an end point. Then an interval between the extracted points A, B is noticed and a new extracted point F (tm2) is added to the segment AE and the AE component of the outline CL. Similarly a new extracted point G (tm3) is added to a segment AF and the AF component of the outline CL. A new extracted point H (tm4) is also added to a segment EB. The coordinate data of the newly added extracted points G, F, H are written in an approximate data memory. Respective extracted points on the segments AG, GF, FE, EH, HB are arranged by distinguishing them as respective start and end points and stored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour line approximation method.

[0002]

2. Description of the Related Art In recent years, in an information processing device such as a word processor, for example, a character or figure written in a document by a user can be taken into the information processing device as an external character by using an image reading device such as an image scanner. It is becoming possible.

Conventionally, in such a case, data is handled as image data as a set of dots in an information processing apparatus. However, there is also a strong demand for converting such image data into vector data for beautiful display or printing.

However, there has been no known means for easily converting image data into vector data.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a useful contour line approximation method when converting image data into vector data.

[0006]

According to the present invention, a finite number of extraction points are defined on the contour line of image data, and two adjacent extraction points are selected from these extraction points. The second step of obtaining the degree of coincidence between the line segment connecting the two extraction points and the contour line, and a new point located between the two extraction points on the contour line until the degree of coincidence reaches a predetermined value. In addition, it has a third step of repeating the process of the second step for the added extraction point and the extraction points adjacent to this extraction point.

[0007]

With this configuration, according to the present invention, the degree of coincidence between the straight line connecting the two extraction points on the contour line of the image data and the contour line is obtained by the means described above, and if the degree of coincidence is smaller than the predetermined value, 2 A new extraction point is required between the points. After that, the degree of coincidence between the straight line connecting one of the two extraction points and the new extraction point and the contour line is obtained. When the above processing is repeated and the degree of coincidence reaches a predetermined value, the straight line connecting the two extraction points at that time becomes an approximate vector of the contour line.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a functional block diagram of an information processing apparatus for carrying out a contour line approximating method according to an embodiment of the present invention. In the figure, 1 is an input unit such as an image scanner, 2 is an image memory for storing the input data from the input unit 1 as image data, 3 is a contour line extracted from the image data in the image memory 2, and the result is a contour. A straight line approximation processing unit 5 having a function of writing in the line memory 4 or calculating the degree of coincidence between a line segment and a contour line stores coordinates of extraction points (start point, end point, approximate point, etc., which will be described later). An approximate data memory 6 is a display data conversion processing unit that converts the data of the extraction points in the approximate data memory 5 into a format that can be displayed on the output unit 8 such as a CRT. A display memory 7 stores the data converted by the display data conversion processing unit 6.

Next, referring to FIG. 2, the outline of the processing for carrying out the contour line approximating method of the present embodiment will be described. First, an arbitrary reading object such as a character or a figure written on a document is read in the input unit 1, and the data is stored as image data in the image memory 2 (step 1). Next, the linear approximation processing unit 3 performs processing such as contour tracing on the image data in the image memory 2 (step 2), represents the contour lines of the image data as a set of many contour points, and draws the contour point group. Write to the contour line memory 4. Then, the data in the contour line memory 4 is subjected to a linear approximation process which will be described in detail later (step 3), and as a result,
A group of extracted points such as a start point, an end point, and an approximation point is written in the approximation data memory 5. Then, the extraction point group in the approximate data memory 5 is passed from the linear approximation processing unit 3 to the display data conversion processing unit 6, and the display data conversion processing unit 6 outputs the approximation result composed of the extraction point group to the output unit 8 Is converted into a format that can be displayed on the display memory 7 and written in the display memory 7, and the data in the display memory 7 is displayed on the output unit 8 (step 4). The contour line approximating method according to the present embodiment can be applied to a case where a user registers an external character, a font updating operation, other graphic data acquisition, and the like.

Next, regarding the above-mentioned straight line approximation processing (step 3 in FIG. 2), referring to the flowchart in FIG.
-It demonstrates, referring FIG. In FIG. 4, CL is a contour line, and this contour line CL is composed of a large number of contour point groups. DT (hatched portion) is an image data portion surrounded by the contour line CL. 4 to 6, the image data part DT is included for the sake of easy understanding of the description, but the image data part DT is not essential for processing, and only the contour point group is extracted. May be processed above.

First, a finite number of extraction points A, B, C, D are set on a given contour line CL, and two adjacent extraction points A, B, C, D are extracted. Select A and B. Specifically, the contour line CL is surrounded by the smallest rectangular frame FM that is in contact with the contour line CL (step a), and these contact points A, B, C, D are extracted (step b). Next, as shown in FIG. 5, line segment AB, line segment BC, line segment C
D, a line segment DA is linearly approximated, and each line segment AB, BC, CD,
The start and end points of DA are stored in the approximate data memory 5 (step c). Here, these line segments AB, BC, C
D and DA are also composed of a set of coordinate points.

First, of the above line segments, attention is paid to the line segment AB, and the coordinate points on the line segment AB are obtained (step d).
Next, the contour points of the AB component in the contour line are obtained, and the line segment AB
The degree of coincidence (the ratio of the number of coincident points) between the number of coordinate points and the contour points of the AB component of the contour line is obtained (step e). Then, the degree of coincidence is compared with a predetermined value (step f), and if the predetermined value is reached, the process proceeds to step h, and if not, the process proceeds to step g. This predetermined value can be changed according to the degree of approximation desired by the user, and may be set to 60%, for example.

Next, with reference to FIG. 6, a process of repeatedly adding a new point on the contour line CL as an extraction point until the degree of coincidence reaches a predetermined value will be described.

At the initial stage, the contact A and the contact B
Focusing on the gap, first, the degree of coincidence was obtained for the AB components of the line segment AB and the contour line CL. However, there are few cases where the contour line CL can be sufficiently approximated by the line segment AB determined at the initial stage, and it is usually necessary to set a new extraction point on the AB component and add this extraction point to the approximation point. As shown in FIG. 6, in the present embodiment, when setting this new contact point, the point E at which the distance between the line segment AB and the AB component of the contour line CL is maximum (tm1) is saved as the end point. (Step g). In this way, the new contact point E
The line segment AE and the line segment EB including the new extraction point E are closer to the AB component of the contour line CL than the approximate line segment AB before the setting of, and the approximation can be advanced. it can.

Next, pay attention to between the extraction points A and E,
A new extraction point F (interval tm2) is added for the AE components of the line segment AE and the contour line CL. Similarly, a new extraction point G (interval tm3) is added for the AF components of the line segment AF and the contour line CL. Further, a new extraction point H (the above-mentioned interval tm4) is added to the line segment EB. Of course, the coordinate data of the newly added extraction points G, F, E, H are written in the approximate data memory 5.

Here, line segment AG, line segment GF, line segment FE,
Assuming that the degree of coincidence between the line segment EH and the line segment HB and the corresponding component of the contour line CL has reached a predetermined value, each of these line segments AG, GF, FE, EH, and HB is extracted. The points are arranged and saved with distinction between the start point and the end point (steps h and i). Such processing is also performed for the line segments BC, CD, and DA, and the contour line approximation method in the linear approximation processing unit 3 is completed.

In this embodiment, when the contour line CL is given, the contact points A, B, C and D on the rectangular frame FM which are in contact with the contour line CL are set as the extraction points in the initial stage. Various modifications can be made such that a group of straight lines forming a predetermined angle with each other from the center of the line CL is radially extended, and an intersection of the group of straight lines and the contour line CL is used as an initial extraction point.

[0019]

According to the present invention, a finite number of extraction points are defined on the contour line of image data, and a first step of selecting two adjacent extraction points among these extraction points and the two extraction points. The second step of obtaining the degree of coincidence between the connecting line segment and the contour line, and adding a new point located between the two extraction points on the contour line to the extraction point until the degree of coincidence reaches a predetermined value. The extraction point and the extraction points adjacent to this extraction point have the third step of repeating the process of the second step. Therefore, the contour line of the image data is smoothly approximated by a finite number of vectors to obtain the vector Can be converted to data.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an information processing apparatus for implementing a contour line approximation method according to an embodiment of the present invention.

FIG. 2 is a flowchart of an image reading method that employs a contour line approximation method according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a contour line approximation method according to an embodiment of the present invention.

FIG. 4 is a process explanatory diagram of a contour line approximating method according to an embodiment of the present invention.

FIG. 5 is a process explanatory diagram of a contour line approximating method according to an embodiment of the present invention.

FIG. 6 is a process explanatory diagram of a contour line approximating method according to an embodiment of the present invention.

[Explanation of symbols]

 1 Input Section 2 Image Memory 3 Linear Approximation Processing Section 4 Contour Line Memory 5 Approximation Data Memory 6 Display Data Conversion Processing Section 7 Display Memory 8 Output Section FM Rectangular Frame

Claims (1)

[Claims] 1. A first step of defining a finite number of extraction points on a contour line of image data and selecting two adjacent extraction points from these extraction points, and a line segment connecting the two extraction points. The second step of obtaining the degree of coincidence with the contour line, and adding a new point on the contour line between the two extraction points to the extraction point until the degree of coincidence reaches a predetermined value A contour line approximation method comprising: a point and a third step of repeating the processing of the second step for the extraction point adjacent to the extraction point.