JP2513365B2 - Contour tracking method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour tracking method for detecting and tracking the contour of a binarized two-dimensional pattern such as characters and figures and obtaining contour line data.

[0002]

2. Description of the Related Art As a method for detecting and tracking the contour of a two-dimensional pattern such as characters and figures, for example, the contour tracking method disclosed in Japanese Patent Publication No. 58-47063 has been proposed. This method prepares a work memory four times as large as the two-dimensional pattern in advance, scans the original pattern, writes the data in the work memory according to a certain rule, and then tracks the contour pixels. In comparison, the feature is that the outer contour and the inner contour can be completely traced even for a closed curve having a line width of 1 pixel. However, in this method, since the contour pixels are tracked, when the image is enlarged and reproduced from the obtained contour data, the line width of the portion having the line width of 1 remains 1 regardless of the magnification. However, there is a drawback that a figure similar to the original image cannot be obtained. In order to improve this point, the image data compression method of Japanese Patent Application No. 3-135492 has been proposed. In the contour tracking method in this image data compression method, a work memory that is larger by one pixel in the vertical and horizontal directions for a two-dimensional pattern is prepared, and a special converted image is created in the work memory. Pixels are tracked, and by performing a special conversion, the tracked contour line data is the original two-dimensional pattern.
The same result as when tracing the boundary line between the on pixel and the off pixel is obtained. However, in order to actually use this method, the off pixel part of 1 pixel width may be crushed by a special conversion. Therefore, first, the original two-dimensional pattern is doubled vertically and horizontally, and then the special conversion is performed. Will be done.

[0003]

However, in the above method, the work memory larger than the two-dimensional pattern must be prepared before the contour tracking is started, and
It is necessary to write special data obtained by scanning the two-dimensional pattern in the prepared work memory,
Contour tracking has the drawback that it is necessary to retrieve the next contour pixel from the current contour pixel.

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a contour tracing method capable of tracing the boundary between on pixels and off pixels at high speed with a small work memory.

[0005]

The present invention solves the above problems by the following or means.

A contour tracking method for receiving a binary two-dimensional pattern of a character, a figure, etc. expressed by on and off of pixels and tracing a boundary between on pixels and off pixels in the pattern as a contour, When the boundary between adjacent pixels having a two-dimensional pattern stored in the pixel memory is a contour, the on or off information of two pixels located immediately in front of the boundary in a predetermined tracking direction is stored in the image memory. Read from the above, and turn on and off the two pixels
It is a contour tracking method that determines the boundary to be tracked next by the combination of.
And

Binary storage means corresponding to a boundary in a predetermined direction among the four boundaries of each pixel of the two-dimensional pattern is provided, and when the boundary is traced as a contour, it corresponds to the traced boundary. The contour tracking method described in (1) above, wherein a tracked mark is written in the storage means.

The boundary for starting contour tracing is the two-dimensional boundary.
Raster scan each pixel of the pattern, and
The boundary of f pixels is detected, and the memory hand corresponding to this boundary is detected.
Read the information on the column and compare the information with the tracked marks.
If they do not match, the contour tracing is started from the boundary.
It is characterized by doing Contour tracking method described in
Law.

[0009]

The present invention will be described below with reference to the drawings. FIG. 1 is a flow chart showing the procedure of processing in the embodiment of the present invention. The process in step 101 is binary 2
Binary storage means (hereinafter referred to as mark storage memory) corresponding to each pixel of a three-dimensional pattern (hereinafter referred to as input image)
Is an initialization process for preparing and initializing. Step 10
At 2, raster scanning is performed on the memory in which the input image is stored. In this raster scan, the coordinate system shown in FIG. 3 is scanned from left to right and from top to bottom. In step 103, a boundary for starting contour tracing is determined. In step 104, contour tracing is executed and the obtained contour data is stored. In the initialization of the mark storage memory in step 101, all the pixels are turned off.

The coordinate system of the input image is as shown in FIG. The four boundaries of each pixel will be described by taking an on pixel 301 as shown in FIG.
2, left boundary 303, lower boundary 304, and right boundary 305
It becomes. FIG. 2 is a flow chart showing an example of the processing performed in step 104 in FIG. Here, first,
The contour tracking start boundary detected in step 103 is stored as the contour starting boundary (201 in FIG. 2), and the contour tracking starting boundary is registered as the current boundary ( 202 in FIG. 2). Next, the current boundary is stored as contour data in the contour data storage memory (203 in FIG. 2). Then, it is checked whether the current boundary is the left boundary (204 in FIG. 2), and if it is the left boundary, the tracked mark is written in the corresponding pixel of the mark storage memory (205 in FIG. 2). Then, the next boundary is determined according to the contour tracking rule (20 in FIG. 2).
6). Here, it is checked whether or not the next boundary matches the contour start boundary (207 in FIG. 2). If they match, the process ends. If they do not match, the next boundary is registered as the current boundary and The process of returning to step 203 is performed.

The contour tracking rule will be described with reference to FIG. When a certain boundary 401 of the input image is traced as a contour (hereinafter referred to as a current contour or a current boundary), the boundary 401 is immediately followed according to a predetermined direction (here, the on pixel is always left). The on / off combination of the two front pixels, that is, the left front pixel 411 and the right front pixel 412 is examined (see FIG. 4).
(A)). Then, according to the rule shown below, the boundary to be traced next as the contour is determined.

A left front pixel 411 and a right front pixel 41
When both 2 are on (FIG. 4B), the boundary 402 connected to the right of the current boundary is set as the next contour.

A left front pixel 411 and a right front pixel 41
When both 2 are off (FIG. 4C), the boundary 403 connected to the left of the current boundary is set as the next contour.

When the pixel 411 on the left front side is on and the pixel 412 on the right front side is off (FIG. 4 (d)), the boundary 404 in the traveling direction with respect to the current boundary is taken as the next contour.

When the pixel 411 on the left front side is off and the pixel 412 on the right front side is on (FIG. 4 (e)), the boundary 40 connected to the right side with respect to the current boundary is determined by a special determination method.
2 or a boundary 40 connected to the left of the current boundary
Either of 3 is set as the next contour. However, as the special determination method, here, the boundary 40 that is always connected in the right direction is used.
Let 2 be the next contour. In addition, as a special judgment method,
Use the on / off state of pixels near the current border and the state of the tracking border to determine when to select the border connecting to the right and when to select the border connecting to the left. Is also good. A method of storing a tracked mark for preventing multiple contour tracking will be described. In the contour tracing process, when the traced contour is the left boundary 303 of the on pixel 301 as shown in FIG. 5A, the corresponding pixel 501 in the mark storage memory is turned on.

The condition of the contour tracking start boundary will be described. Scan each pixel of the input image from left to right, top to bottom,
A boundary satisfying the following conditions is set as a contour tracking start boundary.

Two consecutive pixels in the X-axis direction are off and on
It is the order of.

The pixel of the mark storage memory corresponding to the on pixel of the input image is off.

For simplicity, the value F (x, y) of each pixel of the input image is the value G (x, y) of each pixel of the mark storage memory, where 0 ≦ x ≦ Xmax, 0 ≦ y ≦ Ymax (input image Then, the above condition can be written as follows.

F (x-1, y) = off and F (x, y) = on and G (x, y) = off The input image is scanned in the X-axis direction and is continuously turned off and on. Detecting the boundary of the existing pixel means that the left boundary of the on pixel is detected. Further, the pixel of the mark storage memory corresponding to this on pixel is marked whether or not the left boundary of the on pixel is traced as an outline. Therefore, the contour tracking start boundary can be detected under the above conditions.
However, the left edge of the input image requires a value of F (-1, y), which is always off. Now, the contour tracking end is when the contour tracking start boundary is detected again during the contour tracking. 3 to 7, it is assumed that the black circle represents an on pixel. Based on each operation described above, an embodiment of the present invention will be described with reference to the example diagram shown in FIG. First, a mark storage memory having the same size as the input image is prepared and all pixels are turned off (101 in FIG. 1). The state of the mark storage memory at this time is shown in FIG. And FIG.
The input image of (a) is scanned from left to right and from top to bottom (102 in FIG. 1), and it is determined whether or not it is a contour tracking start boundary (103 in FIG. 1). Therefore, the boundary 601 of FIG. 6B is first detected, and the contour tracking process is started (10 in FIG. 1).
4). Here, first, it is stored that the boundary 601 is the contour tracking start boundary (201 in FIG. 2). Next, the contour start boundary is set as the current boundary (202 in FIG. 2), and the current boundary is stored as the contour data (203 in FIG. 2). Then, it is checked whether the current boundary is the left boundary (204 in FIG. 2).
Since the boundary 601 is the left boundary, the corresponding pixel (701 in FIG. 7B) of the mark storage memory is turned on (205 in FIG. 2). The current boundary 601 according to the contour tracking rule
The pixels on the left and right immediately before the traveling direction of are checked, and the pixel on the left front is on and the pixel on the right front is off, so the next boundary 602 is determined (206 in FIG. 2). Then, boundary 6
02 checks the contour start boundary 601 or the movement, and the boundary 602 and the contour start boundary 601 do not match (see 20 in FIG. 2).
7), the boundary 602 is registered as the current boundary (2 in FIG. 2).
08), and return to 203 in FIG. In this way, the operations 203 to 208 in FIG. 2 are repeated, and the current boundary is changed to that in FIG.
In the case of 603 in (b), when the next boundary 601 is determined according to the contour tracking rule in FIG. 2, the next boundary and the contour start boundary match in 207 in FIG. 2, so the contour tracking processing (104 in FIG. 1). To finish. At this time, the contents of the contour data stored in the contour data storage memory are shown in FIG.
A contour 691 as shown in (c) is obtained. Also,
The mark storage memory is as shown in FIG. Then, returning to 102 in FIG. 1, the scanning of the input image is restarted.
The boundary 611 is detected as the next contour start boundary. FIG. 6D shows the contents of the contour data storage memory when the boundary contour tracing of 104 in FIG. 1 is executed and the tracing is completed. It can be seen that the contour 692 is newly obtained. The state of the mark storage memory is shown in FIG.
It looks like (d). Further, 102 and 10 in FIG.
3 continues scanning the input image and detecting the contour tracking start boundary, and the contour tracking start boundary detected next is shown in FIG.
It becomes 621 of (b). FIG. 6E shows the contents stored in the contour data storage memory when the contour tracking processing of 104 in FIG. 1 is completed. It can be seen that the contour 693 is newly detected. The state of the mark storage memory is shown in FIG. Further, the scanning of the input image and the detection of the boundary for starting contour tracking are performed in 102 and 103 of FIG.
The scanning is ended by 2, and the entire contour tracking processing is ended.

Although the present invention has been specifically described with reference to the embodiment, the present invention is not limited to this embodiment. For example, the contour tracking direction may be such that the on pixel is always on the right, and the scanning method of the input image is right to left, top to bottom, or bottom to top, left to right, or bottom. From top to right, right to left. The contour tracking direction, the scanning method of the input image, the method of writing the tracked mark to prevent the multiple tracking of the contour, the condition of the boundary for starting the contour tracking, and the tracking rule are closely related, so according to the changed condition It suffices to change the method of writing the tracked mark for preventing the multiple tracking of the contour, the condition of the contour tracking start boundary, and the tracking rule.

[0022]

As described above, according to the present invention, the boundary between the on-pixels and the off-pixels of the two-dimensional pattern is traced as the contour. Therefore, the enlarged reproduction of the image is performed based on the obtained contour data. Even if is performed, an image similar to the original two-dimensional pattern is reproduced. The working memory is a memory for writing a tracked mark in order to avoid multiple contour tracking, that is, a binary storage means corresponding to the boundary of each pixel of the original two-dimensional pattern in a predetermined direction. Only needed. Therefore, the required capacity of the work is the same as the original two-dimensional pattern. As described above, by adopting the present invention, contour tracking can be executed with a small working memory. Further, it is not necessary to scan the two-dimensional pattern as a pre-process for contour tracing and write it in the mark storage memory based on the result. Further, in contour tracking, since a boundary to be tracked next can be found by an on / off pattern of two pixels immediately in front of a predetermined direction with respect to the current tracking boundary, high-speed processing is possible. It will be possible.

[Brief description of drawings]

FIG. 1 is a flowchart showing a processing procedure in an embodiment of the present invention.

FIG. 2 is a flowchart showing details of step 104 in FIG.

FIG. 3 is a diagram showing a coordinate system of an input image and boundaries of pixels in the embodiment of FIG.

FIG. 4 is a diagram showing a rule of contour tracking in the embodiment of FIG.

5 is a diagram showing a storage system of a tracked mark in the embodiment of FIG.

FIG. 6 is a diagram illustrating a contour tracking method for an input image in the embodiment of FIG.

7 is a diagram showing the contents of a mark storage memory corresponding to the contour tracking of FIG.

[Explanation of symbols]

301 ... Input image on pixel 302 ... Pixel 301 upper boundary 303 ... Pixel 301 left boundary 304 ... Pixel 301 lower boundary 305 ... Pixel 301 right boundary 401 ... Current boundary 402 ... Right boundary with respect to current boundary Next boundary connected 403 ... Next boundary connected to the left side of the current boundary 404 ... Next boundary connected to the current boundary in the traveling direction 411 ... Pixel immediately left of the current boundary 412 ... Immediately of the current boundary Right front pixel 501 ... Pixel on mark storage memory 601, 611, 621 ... Contour tracking start boundary 691, 692, 693 ... Contour showing the contour stored in the contour data storage memory 701 ... Tracked mark

Claims (2)

(57) [Claims] 1. A contour tracking method for receiving a binary two-dimensional pattern of a character, a figure, or the like represented by on and off of a pixel and tracing the boundary between the on pixel and the off pixel in the pattern as a contour. Then, when the boundary between adjacent pixels having a two-dimensional pattern stored in the pixel memory is a contour, information on or off of two pixels located immediately in front of the boundary in a predetermined tracking direction is provided. Read from the image memory and turn on and off the two pixels
Of the four boundaries of each pixel of the two-dimensional pattern by determining the boundary to be tracked next .
Binary memorizer corresponding to the boundary of a predetermined direction in
A step is provided so that when the boundary is traced as a contour, it is added.
A tracked marker in the storage means corresponding to the traced boundary.
A contour tracking method characterized in that the contour is written . 2. A boundary for starting contour tracking is raster scan of each pixel of the two-dimensional pattern, and an on pixel and of
The boundary of f pixels is detected, the information in the storage means corresponding to this boundary is read out, and when the information and the tracked mark are compared and the two do not match, the contour tracking is started from the boundary. The contour tracking method according to claim 1, which is characterized in that: