JPH0793560A - Graphic contour line recognition method - Google Patents

Abstract

PURPOSE:To easily recognize the contour of the graphic expressed by vector data by determining the angle formed by an already determined contour line element and plural contour line candidate elements having the endpoint which coincides with the element when plural contour line candidate elements exist. CONSTITUTION:One element on a graphic contour line, a straight line AB, for instance, is selected and this straight line AB is defined as a contour line heading element for tracing the graphic contour line. Next, the endpoint which is capable of tracing the graphic in a counterclockwise direction is defined as an endpoint j and the endpoint which is not capable of tracing the graphic is defined as an endpoint i of the both endpoints A and B. A contour line candidate element having a point which coincides with the endpoint j is searched in a figure. When the number of contour line candidate element is 0, it is defined as an error. When the number is 1, the element is defined as a contour line. When the number is more than two, the element which is already determined as the contour line is defined as a base line, the angle formed by the base line and each contour line candidate element in the counterclockwise direction is determine and the contour line candidate element having the smallest angle is determined as the contour line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recognizing a contour line of a figure in a CAD system or the like, and more particularly to a contour line of a figure represented by vector data consisting of straight lines, circles and arcs. The present invention relates to a method of recognizing a figure contour line.

[0002]

2. Description of the Related Art As a method of recognizing the contour line of a figure, for example, Japanese Patent Laid-Open No. 20789/1993 or Japanese Patent Laid-Open No. 5-1 / 1993.
There is a contour figure recognition method as disclosed in Japanese Patent No. 08824.

Among them, the method disclosed in Japanese Patent Laid-Open No. 3-20789 is a method relating to a character generation system different from the CAD system, but the contour line of each element is approximated by a polygon from the skeleton vector character information. In this case, the coordinates of the vertex are calculated, the coordinates of the intersection with the contour of the different element are calculated, and the coordinates of the contour of the entire character are calculated from the calculated coordinates of the intersection and the vertex of the contour of each element extracted. By calculating the columns, the necessary information for generating the contour vector character information is generated.

On the other hand, in the method disclosed in Japanese Patent Laid-Open No. 5-108824, the lowest point among the vertices of a polygon is used as the contour extraction start point, and the search point in the X-axis direction with this start point as the start point. Is rotated counterclockwise, the first overlapping straight line is the first contour straight line, and then the search vector having the end point of the first contour straight line as the origin and the starting point as the end point is rotated counterclockwise, and the first overlapping straight line is obtained. This is a method for extracting a polygonal contour line by sequentially repeating the process of forming the next contour line.

[0005]

By the way, in a CAD system or the like, a graphic is sometimes handled from a combination of a straight line and a circle or a circular arc, and a contour line must be extracted for such a graphic.

However, the method disclosed in Japanese Unexamined Patent Publication No. 5-108824 has a problem that the object is a polygon that does not include a circle or an arc, and a contour line cannot be extracted from a figure including a circle or an arc. is there.

On the other hand, in the method disclosed in the above-mentioned Japanese Patent Laid-Open No. 3-20789, it is stated that contour information is obtained without approximating polygons even in the case of splines and circles. The specific method is not described.

An object of the present invention is to provide a graphic contour line recognizing method capable of easily recognizing a contour line of a graphic represented by vector data consisting of straight lines and circles or arcs.

[0009]

In order to achieve the above-mentioned object, the present invention basically relates to a graphic drawn by a combination of straight lines, arcs and circles, which is vector data, and an outline of the graphic. From the straight line, arc, or circle elements on the line, search for a contour line candidate element with the same end point coordinates, and repeat the processing to determine the contour line element from that element, and repeat the figure contour in a fixed direction. In the method for recognizing a graphic contour line according to step 1, when there are a plurality of contour line candidate elements, the angle formed between the contour line element already determined and the plurality of contour line candidate elements having end points matching the respective elements is determined. When the element having the smaller angle is selected as the contour line element and the angle is obtained, if the elements for which the angle is obtained are straight lines, the angle is obtained from the coordinates of the end points of the two straight lines, and the arcs In the case of an arc and a straight line, a tangent line is drawn from the end point which is the intersection point of the two elements in the direction in which the arc expands, and the angle formed by the two elements is obtained using the end point coordinates of the tangent line instead of the arc. .

Further, when the tangent line is drawn out and there is a straight line that coincides with the tangent line, an arc chord is used instead of the tangent line.

[0011]

According to the above means, when there are a plurality of contour line candidate elements, the angles formed by the contour line element that has already been determined and the plurality of contour line candidate elements having end points that match the element are obtained, The one with the smaller angle is selected as the contour line element. Then, when the angle is obtained, the angle is obtained from the coordinates of the two end points of the straight line if the element for obtaining the angle is a straight line, and if the arc is between arcs or between arcs and a straight line,
A tangent line is drawn from the end point which is the intersection point of the elements in the direction in which the arc expands, and the angle formed by the two elements is obtained using the end point coordinates of the tangent line instead of the arc.

Therefore, it is possible to easily recognize the contour of the figure represented by the vector data consisting of the straight line and the circle or the circular arc.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to illustrated embodiments.

FIG. 1 is a flow chart showing an embodiment of the procedure of the graphic contour recognizing method of the present invention, and FIGS. 2 to 4 are explanatory views. The procedure shown in FIG. 1 is not shown in CAD.
Etc. are executed by a computer.

The concept of the contour line recognition method will be described below with reference to these figures.

First, one element on the contour line of the figure, for example, the straight line AB in FIG. 2 is selected, and this straight line AB is set as the contour head element for tracing the contour line of the figure (step 1).
0).

Next, of the two end points A and B of the first element of the contour line, the end point that can trace the figure in the counterclockwise direction is the end point j, and the other end point is the end point i. In FIG. 2, A is the end point i and B is the end point j (step 1
1).

Next, a contour line candidate element having a point that coincides with the end point j is searched for in the figure (step 12).

Here, the processing is divided as follows depending on the number of contour line candidate elements (step 13).

If the number of contour line candidate elements is 0, it is judged as an error (step 17).

In the case of one, the element is set as the contour line (step 14).

In the case of two or more elements, the angle which the counterclockwise direction makes between the base line and each contour line candidate element is calculated with the element already determined as the contour line as the base line, and the contour line with the smallest angle is obtained. Candidate elements are determined as contour lines (step 1
8).

In the case of FIG. 2, the contour line candidate element is the straight line BC.
And a straight line BD. In this case, angles ∠ABC and ∠ABD formed in the counterclockwise direction with respect to the base line AB are obtained, and ∠ABC having a small angle, that is, the straight line BC is set as the contour line. When the contour line is determined, the end points i and j are also changed. For example, in FIG. 2, when the straight line BC is determined as the contour line, the end point i is changed from A to B and the end point j is changed from B to C (step 15).

When the contour line candidate element is the arc BC as shown in FIG. 3, the arc BC is given as shown in FIG.
Draw a tangent line at the end point j (B) of the arc BC, and create a straight line BF with F as an arbitrary point different from B on the tangent line of the bulging direction of the arc BC, and turn the base line AB and the straight line BF in the counterclockwise direction. The angle formed by is regarded as the angle formed by the base line AB and the arc BC, and the magnitudes of the angles are compared with the angles of other contour line candidate elements.

In this case, ∠ABF and ∠ABC are obtained, and ∠ABF that is the minimum angle, that is, arc BC is used as the contour line.

Of the two end points of the element that has become the contour line, the end point that is already connected to the element that has already been determined as the contour line is the end point i, and the other end point is the end point j (step 1).
5).

After that, all the contour line elements are traced in the same procedure to sequentially determine the contour line, and when the determined element matches the head element, the process is terminated.

FIGS. 5 and 6 are explanatory views showing the process of recognizing the contour line of a more complicated figure, and FIG. 7 is a vector data table TB for all the elements constituting the figure.

The vector data table TB includes the attributes 71 of the graphic element to be the outline, the coordinates 72 of the end point a, the coordinates 73 of the end point b, the coordinates 74 of the center point, the radius 75, and the direction 7 of the arc.
It consists of 6 items, and the data of each element forming the contour line is registered.

Regarding the circular arc, data is registered so that the circular arc extends in the counterclockwise direction from the end point b. Hereinafter, the case of recognizing the contour line of the figure shown in FIG. 5 will be described.

First, the straight line AB is used as a contour line head element for recognizing the contour line, and the figure is traced counterclockwise. At this time, A is an end point i and B is an end point j.

Next, the vector data table TB is searched for an element having a point that coincides with the end point j (B) of the straight line AB.
Then, since only the straight line BC exists, this straight line BC is determined as the contour line. At this time, in the straight line BC, B connected to the straight line AB recognized as a contour line is defined as an end point i, and C is defined as an end point j.

Next, the vector data table TB is searched for an element having a point that coincides with the end point j (C). Then, there are three candidate elements of the arc CD, the straight line CD, and the straight line CI. Therefore, in order to determine which should become the contour line, the straight line BC is used as the base line and the arc CD from the end point j (C) is used.
The angle ∠BCJ, ∠BCD, ∠BCI formed in the counterclockwise direction with the tangent line CJ to the direction in which swells is obtained and compared, and ∠BCJ that is the minimum angle, that is, arc CD is determined as the contour line. To do. At this time, C connected to the straight line BC is set as a new end point i, and D is set as a new end point j.

Next, the vector data table TB is searched for an element having a point that coincides with the end point j (D). Then, since there are two elements of the straight line DE and the straight line DC, the end point j
From (D), ∠KDE and ∠KDC are found in the counterclockwise direction with the tangent line DK to the direction in which the arc CD swells as a base line, and compared, and the minimum angle ∠KDE, that is, the straight line DE
Is determined as the contour line. At this time, on the straight line DE,
Let D, which is connected to the arc CD, be a new end point i, and E be a new end point j.

Next, the vector data table TB is searched for an element having a point that coincides with the end point j (E). Then, there are three elements of arc EF (counterclockwise), straight line EF, and arc EF (clockwise).

Therefore, a tangent line EM and a tangent line EL are drawn from the end point j (E) in the directions in which the arcs swell, and a straight line D is drawn.
∠DEM, ∠DE in the counterclockwise direction with E as the baseline
F and ∠DEL are calculated and compared, and the minimum angle is ∠DEL
That is, the arc EF (counterclockwise) is determined as the contour line.

At this time, in the arc EF (counterclockwise), E connected to the straight line DE is set as a new end point i, and F is set as a new end point j.

Next, the vector data table TB is searched for an element having a point that coincides with the end point j (F). Then, there are three elements of the straight line FG, the circular arc FE (counterclockwise in the direction from F to E), and the straight line FE.

Therefore, a tangent line FO and a tangent line FN are drawn from the end point j (F) in the directions in which the arcs swell, and the tangent line F is obtained.
∠OFG, ∠OF in the counterclockwise direction with O as the baseline
N and ∠ OFE are calculated and compared, and ∠OFG that has the smallest angle
That is, the straight line FG is determined as the contour line.

Thereafter, similar processing is repeated to recognize the contour line, and the straight line GH, the straight line HI, and the straight line IA are set as the contour lines. Finally, the portion shown by the thick line in FIG. 5 is recognized as the contour line.

Next, the case of recognizing the outline of the figure shown in FIG. 6 will be described.

First, as in the case of FIG. 5, the straight line AB is set as the first element of the contour line for recognizing the contour line, and the figure is traced counterclockwise.

The process up to the point where the straight line DE is recognized as the contour line is the same as in the case of FIG.

At this time, in the straight line DE, D connected to the circular arc CD is the end point i and E is the end point j.

Next, the vector data table TB is searched for an element having a point that coincides with the end point j (E). Then, there are three elements of the arc EF ₂ , the arc EF ₁ , and the straight line EF ₁ .

Therefore, a tangent line EM and a tangent line EL are drawn from the end point j (E) in the directions in which the arcs swell, and a straight line D is drawn.
∠DEM, ∠DE in the counterclockwise direction with E as the baseline
L and ∠DEF ₁ are calculated and compared, and the minimum angle is ∠DE
M, that is, the arc EF ₂ is determined as the contour line. At this time,
In the arc EF ₂ , E connected to the straight line DE is a new end point i, and F ₂ is a new end point j.

Next, an element having a point that coincides with the end point j (F ₂ ) is searched from the vector data table TB. Then,
There are two elements, a straight line F ₂ G and a straight line F ₂ F ₁ .

Therefore, a tangent line F ₂ N is drawn from the end point j (F ₂ ) in the direction in which the arc bulges, and ∠NF ₂ G and ∠NF ₂ F ₁ are set in the counterclockwise direction with the tangent line F ₂ N as the base line. The obtained angles are compared and the ∠NF ₂ G that is the minimum angle, that is, the straight line F ₂ G is determined as the contour line.

Thereafter, similar processing is repeated to recognize the contour line, and the straight line GH, the straight line HI, and the straight line IA are set as the contour lines.

Finally, the portion indicated by the thick line in FIG. 6 is recognized as the contour line.

By the way, when the tangent line of the arc is drawn, for example, in the figure as shown in FIG. 8, the tangent line DH of the end point D of the arc DE and the straight line DG coincide with each other, and therefore the contour line is determined by merely comparing the angles. become unable.

In the case of such a figure, the chord D of the arc DE
Use E instead of tangent line DH and make an angle ∠C with baseline CD
DE and ∠CDG are calculated and compared, and the minimum angle is ∠CD
E, that is, the arc DE is determined as the contour line.

Finally, the portion shown by the thick line in FIG. 9 is recognized as the contour line.

[0054]

As described above, according to the present invention, when there are a plurality of contour line candidate elements, a contour line element that has already been determined and a plurality of contour line candidate elements having end points that match the element are detected. Angle is determined, the smaller one is selected as a contour line element, and when the angle is determined, if the elements for which the angle is determined are straight lines, the angle is determined from the coordinates of the end points of the two straight lines, In the case of arcs or between arcs and straight lines, draw a tangent in the direction in which the arc expands from the end point that is the intersection of the two elements, and use the end point coordinates of the tangent instead of the arc to find the angle between the two elements. Therefore, it is possible to easily recognize the contour of the figure represented by the vector data composed of the straight line and the circle or the circular arc.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of a procedure of a contour line recognition method of the present invention.

FIG. 2 is an explanatory diagram showing how to trace a figure and the positions of end points i and j.

FIG. 3 is a diagram showing a figure composed of straight lines and circular arcs.

FIG. 4 is an explanatory diagram showing a method of discriminating an element that is a contour line in the case of a figure composed of a straight line and a circular arc.

FIG. 5 is an explanatory diagram showing a method of discriminating an element that becomes a contour line when both ends of an arc match.

FIG. 6 is an explanatory diagram showing a method of discriminating an element that is a contour line when one end of an arc matches and one arc is included in the other arc.

FIG. 7 is a configuration diagram of a vector data table.

FIG. 8 is an explanatory diagram showing a method of discriminating an element serving as a contour line when a straight line that matches a tangent line of an arc exists.

9 is an explanatory diagram showing contour lines of the figure in FIG. 8;

[Description of Codes] TB ... Vector data table, 71 ... Attribute, 72 ... Coordinates of end point a, 73 ... Coordinates of end point b, 74 ... Coordinates of center point, 75 ... Radius, 76 ... Direction of arc.

Claims (2)

[Claims] 1. A contour line whose endpoint coordinates match from a straight line, arc or circle element on a contour line of a figure drawn by a combination of straight lines, arcs and circles which is vector data. The process of searching for candidate elements and discriminating the element that becomes the contour line from the elements is sequentially repeated.
In a figure contour line recognition method for tracing a figure contour in a certain direction, when there are a plurality of contour line candidate elements, a contour line element that has already been determined, and a plurality of contour line candidate elements having endpoints that match the element are provided. When each of the angles formed by the two is calculated, the smaller one is selected as the contour line element, and when the angle is calculated, if the elements for which the angle is calculated are straight lines, 2
The angle is calculated from the coordinates of both ends of the straight line, and when the arcs are between the arcs or between the arcs and the straight line, the tangent line is drawn from the end point that is the intersection of the two elements in the direction in which the arc expands, and the end point coordinates of the tangent line are used instead of the arc. A method for recognizing a graphic contour line, characterized in that an angle formed by two elements is obtained. 2. The method for recognizing a graphic contour line according to claim 1, wherein when the tangent line is drawn out and there is a straight line that matches the tangent line, a chord of an arc is used instead of the tangent line.