JP2813059B2 - Position data approximation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position data approximation method for approximating position data of a point sequence using a function.

[Conventional technology]

2. Description of the Related Art In general, reading shapes of characters, figures, and the like with an image reader and reproducing them on a CRT, paper, or the like has been actively performed.

In this case, an outline font is used to read only the position data of outlines of characters, figures, and the like, and reproduce the portion surrounded by the outlines as characters, figures, and the like.

The graphic processing using such an outline font captures the outline of a character, a graphic, or the like as a point sequence and reads or reproduces it.Today, without using the position data of the original graphic as it is, Approximate position data obtained by approximating this using an arbitrary function is used. This is because the position data of the original figure generally requires a large capacity when stored in a memory because of a large change, and a long time is required for various data processing and a long time is required for reproduction. By approximating this using, for example, an arbitrary cubic function, the position data can be compressed, the storage capacity can be reduced, various data processing can be speeded up, the reproduction time can be shortened, and it is almost equivalent to the original figure. Can be reproduced.

In the conventional approximation method, all connection points between a straight line and a curve are obtained, and each approximation section divided by these connection points is approximated using an arbitrary function.

[Problems to be solved by the invention]

However, conventionally, when determining an approximate section to be approximated using a function, all connection points are employed as points for determining the section. Therefore, when the approximate position data is reproduced, the connection points of adjacent approximate sections are determined. However, there was a problem that the joining condition in the above was not theoretically smooth, and when it was remarkable, it was sharply angled.

SUMMARY OF THE INVENTION The present invention has been made in view of these points, and makes it possible to smoothly join approximate position data of adjacent approximate sections, and to reproduce the original figure while maintaining the approximate accuracy with respect to the position data of the original figure at a predetermined value. It is an object of the present invention to provide a method of approximating position data that can be performed.

[Means for solving the problem]

The position data approximation method of the present invention, the position data of the point sequence shape, the point sequence shape is divided into a plurality of approximation sections, and approximated using a function within each approximation section as approximate position data,
In a position data approximation method for smoothing a connection between a straight line and a curve, a step of extracting a candidate of a boundary point to be a connecting portion between the straight line and the curve, and If the included angle is equal to or greater than a first predetermined value, the corresponding boundary point is left as a candidate for a boundary point. If the line segment ratio between the straight line and the curve is equal to or greater than a second predetermined value, the corresponding boundary point is set as the boundary point. A step of leaving as a candidate, a step of leaving a boundary point corresponding to a case where the entire shape of the straight line and the curve has convexity as a boundary point candidate, and a step of approximating with an approximate section delimited by the remaining boundary point. It is characterized by having.

(Operation)

According to the present invention, when an approximate section is divided by a boundary point in order to connect a straight line and a curve, first, a candidate for a boundary point which is a connection between the straight line and the curve is extracted, and then, the extracted boundary point candidate is On the other hand, when the included angle between the straight line and the curve is equal to or larger than the first predetermined value, the corresponding boundary point is left as a boundary point candidate, and when the line segment ratio between the straight line and the curve is equal to or larger than the second predetermined value, The relevant boundary point is left as a boundary point candidate, and then, when the overall shape of the straight line and the curve has convexity, the relevant boundary point is left as a boundary point candidate, and then an approximation separated by the remaining boundary points In order to approximate with a section, a straight line and a curve are joined very smoothly at a boundary point.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a flowchart showing a method of selecting a boundary point according to an embodiment of the present invention, which will be described in order.

First, when selection of a boundary point starts, step ST ₁
In, a boundary point candidate is extracted. This boundary point candidate covers all connection points between a straight line and a curve.

Next, whether or not the boundary points are determined according to ST ₄ from Step ST _2.

That is, in step ST _2, the magnitude of the included angle between the straight line and the curve is determined whether a predetermined value or more at the boundary point candidate, further then step not less than a predetermined value
To proceed to judgment ST _3. In this step ST _2, examine the smoothness of transition from straight to curved, those that are not smooth are removed from the boundary point candidates proceeds to step _6. To further explain with reference to FIG. 2, the boundary point candidate P1 in FIG. 2A and the boundary point candidate P2 in FIG.
One point P1 continues to be a boundary point candidate, and the other point P2
Are removed from the boundary point candidates. In this case, it can be easily determined by obtaining the inner product (cos) of the angle between the straight line and the curve and comparing the obtained value with a predetermined value.

In step ST _3, the ratio of line segment lengths of the lines and curves across the boundary point candidate is determined whether a predetermined value or more, more than the predetermined value to further determine the next step ₄ If it does not exceed the predetermined value, it proceeds to step ₆ and is removed from the boundary point candidates. In this step ST _3, each line segment lengths of the lines and curves across the boundary point candidates,
This is because if one is very short with respect to the other, even if the point is obtained as an approximate section point as a boundary point, a good connection processing effect cannot be obtained. To further explain with reference to FIG. 3, when judging boundary point candidates P3 and P4 between FIGS. 3A and 3B, it is the ratio of the length of a short line segment to a long line segment.
L1 / L2 and L3 / L4 are obtained, and whether or not L1 / L2 is larger than a predetermined value k is calculated. In FIG. 3, one point P3 continues to be a boundary point candidate, and the other P4 is removed from the boundary point candidates.

In step ₄ , it is determined whether or not the entire shape of the straight line and the curve sandwiching the boundary point candidate has convexity.
Those having convexity proceed to the next step ₅ further,
Those having no convexity proceed to step ₆ and are removed from the boundary point candidates. In this step ST _5, if is because connection state becomes smooth compared with the case without a convexity that the overall shape of the lines and curves across the boundary point candidate is provided with a convexity. To further explain with reference to FIG. 4, when judging boundary point candidates P5 and P7 between FIGS. 4A and 4B, a line segment 1 extending in a curved direction from a straight line and boundary point candidates P5 to P6 or The relationship between the curve 2 from P7 to P8 and the line segment 3 connecting both boundary point candidates P5 to P6 or P7 to P8 is convex when line segment 2 is located between line segments 1 and 3. It is determined that there is a possibility. In FIG. 4, one point P5
Is continued as a boundary point candidate, and the other point P7 is removed from the boundary point candidate.

Then proceeds to step ST _5, memorize the point it is determined that the boundary point candidate as a boundary point in step _4.

Then the program proceeds to step ST _7, whether the determination with respect to all the boundary point candidate been finished is determined. If not completed, the determination from step ₂ is repeated, and if completed, the extraction of the boundary point ends.

As described above, according to the present embodiment, when the point sequence shape has a boundary point where a straight line and a curve are connected, only boundary point candidates that make the approximation accuracy of the approximate position data to the position data a predetermined value are used. Adopted as boundary points and approximated by approximation sections delimited by those boundary points, the reproduced approximate figure has a very smooth connection between straight lines and curves.

Further, the boundary point obtained by the present invention is added to the inflection point and the extreme value point obtained from the position data to improve the approximation accuracy, and an approximate section is set. As shown in FIG. 5, when compared with the reproduced figure obtained by the conventional method, which is obtained by the approximate section demarcated only by the connection point between the straight line and the curve shown in FIG. 6, the approximation accuracy is remarkably superior. Recognize.

Note that the present invention is not limited to the above embodiment, and can be modified as needed.

〔The invention's effect〕

Since the position data approximation method of the present invention is constructed and operated in this way, it is possible to smoothly join the approximate position data of adjacent approximation sections, and to set the approximation accuracy for the position data of the original figure to a predetermined value. Thus, it is possible to obtain the effect of being able to hold and reproduce the image.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a case of approximation by the position data approximation method of the present invention, FIGS. 2 (a) and 2 (b) are explanatory diagrams of the determination of the included angle, and FIGS. FIG. 4 (b) is an explanatory diagram for judging the magnitude of the line segment ratio, FIGS. 4 (a) and 4 (b) are explanatory diagrams for judging convexity, FIG. 5 is a reproduction diagram approximated by the method of the present invention, FIG. FIG. 3 is a reproduction diagram of data approximated by a conventional method.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06T 5/00 G09G 5/24 620

Claims (1)

(57) [Claims] 1. The position data of a point sequence shape is divided into a plurality of approximation sections of the point sequence shape, and approximated by using a function in each approximation section to obtain approximate position data, and a connection between a straight line and a curve is smoothed. Extracting a candidate of a boundary point to be a connecting portion between a straight line and a curve, wherein an angle between the straight line and the curve is set to a first predetermined value with respect to the extracted boundary point candidate. In the above case, the step of leaving the corresponding boundary point as a boundary point candidate, and the line segment ratio between a straight line and a curve
A step of leaving the corresponding boundary point as a candidate for a boundary point if the predetermined value is equal to or more than a step of leaving the corresponding boundary point as a candidate for a boundary point when the entire shape of the straight line and the curve has convexity. Approximating with an approximation section delimited by a boundary point.