JP2001243469A - Method for extracting heavy line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing method by which heavy lines are extracted from image data. SOLUTION: This heavy-line extracting method consists of a first stage for extracting a heavy line from the image data and a second stage for shaping the extracted thick line. By the heavy-line extracting method of the first stage, an area filter is used after the image data are binarized and degenerated, and while this area filter measures the area of an isolated figure in the image, the circumscribed rectangle is found from the minimum diameter and outline of the isolated figure; and those values are used as a band to evaluate the filtering, thereby extracting the heavy line. The heavy-line shaping method as the second stage makes the extracted heavy line thin, the heavy line is redrawn by using a catheter method, and the extracted thick line is shaped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image processing method for extracting a thick line from image data.

[0002]

2. Description of the Related Art A conventional method of extracting a thick line will be described with reference to a flowchart of FIG. In the conventional method for acquiring a thick line, image data (step S1) is used.
01) is binarized (step S102), contracted (step S103), and expanded (step S10).
4) A thick line was extracted using an area filter (step S105) (step S106).

[0003]

In the method of obtaining a thick line according to the prior art, in the extraction of a thick line, information is temporarily lost due to "shrinkage", the shape is distorted in the "expansion" process, and large noise is generated in the thick line. There was a problem of becoming.

[0004]

The method for extracting a thick line according to the present invention comprises a first step of extracting a thick line from image data and a second step of shaping the extracted thick line. In the method of extracting a thick line, which is the first step, the image data is binarized and then subjected to degeneration processing, and then an area filter is used.
A thick line is extracted by obtaining the minimum diameter of the isolated figure and the size of a circumscribed rectangle from the contour, and evaluating the filtering using these values as a band. In the method of shaping a thick line, which is the second step, the extracted thick line is thinned, the thin line is redrawn using the catheter method, and the extracted thick line is shaped.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first step, a method of extracting a thick line, a thin line is separated from the thick line by binarizing the image data, reducing the binary image, and using an area filter. And then extract the thick line. That is, the thin line is cut off from the outside of the thick line by using the degeneration method, and the noise and the thin line of the image data are removed by the area filter to extract the thick line. By performing the area filter after the reduction processing, the processing time required for the area filter can be reduced. In general, an area filter measures the area of an isolated figure on a screen, makes a filtering decision using the value as a band, and makes the shape a two-dimensional filter. Therefore, if the target figure is a thin line, the area alone is sufficient. It is not a good index, and thin lines cannot be removed. Therefore, in the area filter according to the present invention, a thin line is removed and a thick line is extracted by adding the evaluation of the minimum area and the size of the circumscribed rectangle to the evaluation based on the “area”, thereby speeding up the processing. For example, when evaluating the area for one isolated figure, if it happens to be connected to another isolated figure, it is naturally determined that these connected figures are one. Therefore, when the evaluation is performed only for the area, the areas of the connected figures are summed up, and the correct evaluation may not be performed. Therefore, in the area filter according to the present invention, the minimum diameter of the isolated figure is simultaneously obtained when the area is obtained, and when the minimum diameter is smaller than a certain value, two or more figures (combined figures) are obtained.
The noise and the thin line are removed from the image data, and the thick line is extracted. Also,
In the area filter, since the logical operation is performed on the image using the extracted shape of the isolated figure itself as a masking pattern, the processing speed can be improved by performing the range of the logical operation with a rectangle circumscribing the isolated figure. Therefore, in the area filter according to the present invention, when obtaining the area, the minimum value and the maximum value of the coordinates of the outline of the isolated figure are simultaneously obtained as the coordinates of the circumscribed rectangle, thereby speeding up the logical operation on the image.

[0006] In the second step, a method of shaping a thick line, the extracted thick line is thinned, a smooth thick line having a line width of 2r is redrawn along the thin line using the "catheter method", and the extracted thick line is shaped. I do. The thinning uses a general skeleton method. Therefore, the pixels on the thin line obtained by thinning are always inside the original thick line, and the distance between the pixel on the thin line and the contour line of the original thick line is 以下 or less of the line width. This means that a circle inscribed in the original thick line can be drawn around the pixel on the thin line. Therefore, by drawing a solid circle having a radius r along the thin line, a smooth thick line having a line width 2r along the thin line is redrawn. FIG. 1 illustrates a method for redrawing a thick line according to the present invention. As shown in FIG. 1A, in the method of redrawing a thick line by the “catheter method”, a circle is drawn centering on the pixel on the thin line while referring to the original thick line, and inscribed with the outline of the original thick line. The radius r is increased until it becomes a circle. By painting the inside of the inscribed circle thus obtained and repeating this processing along the fine line, a smooth thick line having a line width 2r along the fine line can be redrawn. The way to redraw this thick line is
It is called "catheter method" because it looks as if the balloon is inflated through a catheter in a thick line. FIG.
(B) shows a method of drawing an inscribed circle of a contour line by the “catheter method”. When the radius r is gradually increased and a state occurs in which one of the contours is cut off, the coordinates of the intersection of the circle and the contour are (r, θ1) and (r, θ2), respectively.
In this state, the center of the circle is moved by one pixel in the direction of θ = (θ1 + θ2) / 2 + π [radian], the drawing of the circle is tried again, and the drawing is repeated until the drawn circle becomes the inscribed circle of the thick outline.
In other words, if only one side of the circle touches the outline of the thick line, move the center of the circle by the unit length to the opposite side of the contact on the straight line connecting the center of the circle and the contact point, and refer to the original thick line again While drawing a circle, get the inscribed circle of the outline. As described above, a smooth thick line having a line width of 2r along a thin line can be redrawn using the “catheter method”, and the thick line can be shaped.

A method for extracting a thick line according to the present invention will be described with reference to the flowchart of FIG. The method for extracting a thick line according to the present invention includes two processes of “extraction” and “shaping” of the thick line. That is, image data (step S1)
Is binarized (step S2), a thin line is separated from the thick line by performing a reduction process (step S3), and noise and thin lines of the image data are removed using an area filter (step S4), and the thick line is extracted (step S4). Step S5). Next, the extracted thick line is thinned (step S6), the thick line is redrawn using the “catheter method” (step S7), and the extracted thick line is shaped (step S8).

[0008]

As described above, in the method for extracting a thick line according to the present invention,
The method comprises a first step of extracting a thick line from image data and a second step of shaping the extracted thick line. In the first step, after binarizing the image data, performing degeneration processing, and performing area filtering, In the filter, at the same time as measuring the area of the isolated figure on the screen, the minimum diameter of the isolated figure and the size of the circumscribed rectangle from the contour are determined, and the filtering is evaluated using these values as a band to obtain an image. Remove noise and thin lines from the data and extract thick lines at high speed. In the second step, the extracted thick line is thinned,
The thin line is redrawn using a catheter method to redraw the thick line, and the extracted thick line is shaped. That is, in the method of extracting a thick line according to the present invention, the thick line is extracted without causing information loss or shape distortion, and even if there is a defect inside the thick line,
Noise is removed by shaping the thick line. Therefore, the method for extracting a thick line according to the present invention is effective for an operation of acquiring information about a thick line such as a distribution line from map data.

[Brief description of the drawings]

FIG. 1 is a method for redrawing a thick line according to the present invention.

FIG. 2 is a flowchart of a method for extracting a thick line according to the present invention;

FIG. 3 is a flowchart of a conventional method for extracting a thick line.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Endo 6-19-15 Shimbashi, Minato-ku, Tokyo TEPCO Software Corporation (72) Inventor Masahiro Ishikawa 1-9-9 Motohongo-cho, Hachioji-shi, Tokyo No. Chuo Denshi Co., Ltd. (72) Inventor Mitsuhiro Aoki 1-9-9 Motohongo-cho, Hachioji-shi, Tokyo Central Japan Co., Ltd. (72) Inventor Koki Ito 1-9-9 Motomotogo-cho, Hachioji-shi, Tokyo No. 9 Chuo Denshi Co., Ltd. F term (reference) 5B057 CA08 CE12 CF01 CF02 DA08 DA17 DB02 DB08 DC04 5B080 EA04 5C076 AA40 BA06 5L096 AA06 DA01 EA43 FA03 FA18 FA59 FA62 GA55 9A001 HH28

Claims (2)

[Claims] 1. An image processing method for extracting a thick line from image data, comprising the steps of: binarizing image data, performing degeneration processing, and using an area filter; Simultaneously with the measurement, the minimum diameter of the isolated figure and the size of the circumscribed rectangle from the contour are obtained, and the filtering is evaluated using these values as a band to extract a thick line, and the extracted thick line is redrawn. A method for extracting a thick line, comprising shaping and extracting a shaped thick line from image data. 2. An image processing method for redrawing and shaping an extracted bold line, thinning the extracted bold line, drawing a circle around the thin line with reference to the original bold line, and extracting a circle from the outline of the bold line. The radius r is enlarged until it becomes a tangent circle, the inside of the obtained inscribed circle is painted out, and this process is repeated along the thin line to redraw and shape a smooth thick line having a line width 2r along the thin line. 2. The method for extracting a thick line according to claim 1, wherein a catheter method is used.