JPH08110947A - Image thinning processing method - Google Patents

Abstract

PURPOSE: To improve the thinning processing result and to speed up the processing by storing an object picture element as it is when the picture element is matched with a specific condition. CONSTITUTION: An index picture element value '-1' which can not exist in an image is previously defined. When an object picture element A is the index picture element value, the picture element A is set up to a peripheral picture element value (of a picture element not to be processed). When the object picture element A is not the peripheral picture element value or the index picture element value, the following condition is adopted. When the upper and left picture elements of the object picture element A have the peripheral picture element value, the picture element A is stored as it is. A picture element B above the picture element A has the index picture element value and picture elements C1, C2 on the right and left sides of the picture element B have the peripheral picture element value, the object picture element A is set up to the index picture element value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention According to the present invention, a pixel value which is not a processing target is set in advance as a peripheral pixel value, and a figure which is not a peripheral pixel in an image is continuously formed with the shape feature of the figure remaining. In order to be converted into a curve of the pixel width, the pixels which are judged by the parallel type and are not end points or independent points and which are judged by the sequential type and the number of connections is 1 and which are judged by the parallel type as the boundary pixels are The present invention relates to an image processing method for changing the pixel value around a figure.

[0002]

2. Description of the Related Art For example, in a microscopic image of a crystal structure, a crystal interface appears as a curve having a certain width, and in analyzing the crystal structure, this curve must be corrected to a curve having a width of one pixel passing through the center of the curve to obtain the grain size. Can not be measured.
At this time, it is necessary to thin the curve of the interface to one pixel width. If the curve of the interface becomes discontinuous during thinning, adjacent crystal grains will be connected and accurate particle size measurement cannot be performed. Based on this need, there is an almost established demand for thinning.

That is, (1) the line width becomes 1. (2) The position of the line is almost at the center of the original figure. (3) The continuity of figures is preserved. (4) The end portion of the line figure does not shrink more than necessary. (5) No whiskers occur due to the unevenness of the boundary. (6) Lines are not distorted at the intersection of figures.

Among these conditions, the conditions (1) to (4) are called basic conditions for thinning processing, and must be taken into consideration when constructing an algorithm. (Junichi Hasegawa et al .: Basic techniques for image processing, Technical Review, 1961,
The conventional HILDITCH has been used as an image processing method for thinning.
Method is known, and the evaluation of the processing result has been high. However, the HILDITCH method has a problem that the processing speed is insufficient because not only the number of connected target pixels but also the number of connected pixels surrounding the target pixel is evaluated.

As a method for solving the above problems, the method described in JP-A-64-13680 is known. However, in this method, when processing a straight line (FIG. 1) that changes from a width of 3 pixels to a width of 2 pixels and a width of 2 pixels to a width of 1 pixel, only the last pixel of the straight line of 1 pixel remains and the figure disappears. There was a drawback to do.

[0006]

The present invention was devised to solve such conventional problems, and provides an image processing method in which the thinning processing result is good and the processing speed is high. The purpose is to

[0007]

According to the image thinning method of the present invention, the processing of the end points is performed in a parallel type to prevent a "whisker" from remaining behind in the scanning direction, and further, in the parallel direction of the scanning lines. Paying attention to the processing of a straight line in which the number of pixels changes from 3 pixel width to 2 pixel width, from 2 pixel width to 1 pixel width, a straight line in which the number of pixel changes from 3 pixel width to 2 pixel width and from 2 pixel width to 1 pixel width When it is confirmed that it is a straight line in which the pixel value of the target pixel is set as an index pixel value and the number of pixels changes from 3 pixel width to 2 pixel width and from 2 pixel width to 1 pixel width In addition, the pixel positioned diagonally to the lower right of the index pixel is left, and the pixel having the index pixel value is changed to the surrounding pixel value in the next scanning.

[0008]

According to the image thinning method of the present invention, 3
When there is a possibility that a straight line in which the number of pixels changes from the pixel width to the 2 pixel width and from the 2 pixel width to the 1 pixel width occurs, the pixel value of the target pixel is set as an index pixel value, and the 3 pixel width to the 2 pixel width, Two
When it is confirmed that the number of pixels changes from one pixel width to one pixel width, the pixel positioned diagonally below and right of the index pixel is left. It can be changed to surrounding pixel values.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one of image thinning methods according to the present invention will be described.
An embodiment will be described with reference to the drawings. FIG. 9 shows an example of an apparatus for carrying out the present invention. The apparatus is composed of, for example, a central processing unit CPU, an image processing unit IPU and an image memory IM. Central processing unit CPU, image processing unit IPU
The image memory IM is connected via the system bus SB, and the image processing unit IPU and the image memory IM are connected via the local bus LB.

In the preferred embodiment, a typical left-to-right, top-to-bottom scan order is employed. According to the present invention, a pixel that is not a processing target is determined in advance as a peripheral pixel value (for example, “0”), and a graphic that is not a peripheral pixel value in the image is consecutive 1 with the shape feature of the graphic remaining.
In order to convert to a curve of pixel width, it is judged in parallel type and not in end points or independent points, and in sequential type, the number of connections is 1
And a method of changing the pixels that are the boundary pixels to the pixel values around the figure by judging in parallel, and the index pixel value that cannot exist in the image (cannot exist in the image A pixel value, for example, “−1”) is defined, pixels in the image are sequentially scanned to be the target pixel A, and when the target pixel A is an index pixel value, the target pixel A is set as a surrounding pixel value. , When the pixel value is not the surrounding pixel value or the index pixel value, the following condition is adopted in the 3 × 3 convolution.

When the upper and left pixels of the target pixel A have peripheral pixel values, the target pixel A is given an index pixel value different from the normal pixel value (FIG. 3). In the case where the condition is not met, the pixel C above the target pixel A is an index pixel value, which is determined by the sequential type.
When the lower pixel B has a peripheral pixel value, the target pixel A is stored as it is (FIG. 4).

When the condition of is not met,
When the pixel C on the left of the target pixel A has the index pixel value and the pixel B on the right has the peripheral pixel values, the target pixel A is stored as it is (FIG. 5). When the condition C does not match, the pixel C on the left diagonal of the target pixel A has an index pixel value, and the pixel B on the lower right of the target pixel A has surrounding pixel values, The target pixel A is saved as it is (FIG. 6).

When the conditions (1) to (4) are not met, the pixel B on the target pixel A is an index pixel value when judged by the sequential type, and the pixels B on the left and right of the pixel B when judged by the parallel type. When C1 and C2 are surrounding pixel values, the target pixel A
Is an index pixel value (FIG. 7). If the conditions are not met, the pixel B on the left of the target pixel A is an index pixel value, and the pixels C1 and C above and below the pixel B are judged by the parallel type.
When 2 is the surrounding pixel value, the target pixel A is set as the index pixel value (FIG. 8).

The above-mentioned parallel type processing is to judge a pixel whose pixel value has changed the same time in one scanning as if it has not changed, and to perform a sequential type processing. Means that a pixel whose pixel value has changed in one scan is evaluated based on the pixel value after the change. Then, the pixel having the index pixel value generated by such processing is set as the pixel value of the surroundings in the next scanning.

Now, the present invention is applied to the figure of FIG. 1, that is, a figure having a straight line having a width of 3 pixels to 2 pixels and a width of 2 pixels to 1 pixel. Pixel A corresponds to the condition and becomes an index pixel value. Pixels a, u, and d do not correspond to the conditions of-and become the surrounding pixel values. Pixel O meets the condition of
It will be saved as is. By saving the pixel
Pixel power is judged sequentially and the number of connections becomes 2 and is stored.
Similarly, the pixel key and the pixel key are sequentially determined and the number of connections is 2, and they are stored. Pixel image is judged as a parallel type and is an end point and is saved. As a result, the figure in FIG. 1 becomes the figure in FIG. 2 as a result of the thinning process, and the thinned figure can be secured.

In the above process, the central processing unit CPU determines whether or not the target pixel satisfies each condition, and the image processing unit IPU processes the target pixel based on the determination result. Is stored in the image memory IM.

[0017]

As described above, according to the present invention, the processing of the end points is performed in parallel to prevent the "whiskers" from being left behind in the scanning direction, and further, from the width of 3 pixels to 2 in the parallel direction of the scanning lines. Pay attention to the processing of the straight line in which the number of pixels changes from the pixel width of 2 pixels to the width of 1 pixel, and a straight line in which the number of pixels changes from 3 pixel width to 2 pixel width and from 2 pixel width to 1 pixel width may occur. When it is confirmed that the pixel value of the target pixel is set as an index pixel value when the line is a straight line in which the number of pixels changes from 3 pixel width to 2 pixel width and 2 pixel width to 1 pixel width, The pixels located diagonally below and to the right of are left, and the pixels of the index pixel value are changed to the surrounding pixel values at the next scanning,
A figure having a straight line in which the number of pixels changes from 3 pixel width to 2 pixel width and 2 pixel width to 1 pixel width along the parallel direction of scanning lines can be thinned to 1 pixel width without erasing. Has the effect of high speed.

[Brief description of drawings]

FIG. 1 is a drawing to be thinned.

FIG. 2 is a diagram in which the graphic of FIG. 1 is subjected to thinning processing.

FIG. 3 is a conceptual diagram showing judgment conditions.

FIG. 4 is a conceptual diagram showing judgment conditions.

FIG. 5 is a conceptual diagram showing determination conditions.

FIG. 6 is a conceptual diagram showing judgment conditions.

FIG. 7 is a conceptual diagram showing determination conditions.

FIG. 8 is a conceptual diagram showing determination conditions.

FIG. 9 is a block diagram of an apparatus for implementing the present invention.

[Explanation of symbols]

A, B, C, C1, C2, A, B, C, C, C, C, C,
Pixel CPU CPU Central processing unit IPU image processing unit IM image memory SB system bus LB local bus

Claims (1)

[Claims] 1. A pixel which is not a processing target is determined in advance as a surrounding pixel value, and a figure having no surrounding pixel value in the image is converted into a continuous 1-pixel-wide curve while leaving the shape feature of the figure. As described above, it is determined by the parallel type that it is not an end point or an independent point, the sequential type is determined, and the number of connections is 1 and the parallel type is determined, and a pixel that is a boundary pixel is a pixel value around the figure. In the image processing method of changing to, the index pixel value that cannot exist in the image is defined, the pixels in the image are sequentially scanned to be the target pixel, and when the target pixel is the index pixel value, , When the target pixel is the surrounding pixel value and is not the surrounding pixel value or the index pixel value, 1) Judgment by the parallel type and the pixel one pixel before the target pixel and the scanning in the traveling direction of one scanning line About the direction parallel to the line When the pixel corresponding to the position of the target pixel in the contour line is the surrounding pixel value or the index pixel value, the target pixel is converted into the index pixel value, and the condition 2) 1) is not met, The pixel corresponding to the position of the target pixel in the scanning line one before in the parallel direction of the scanning lines is the index pixel value determined by the sequential type, and the scanning line one after in the parallel direction of the scanning lines. When the pixel corresponding to the position of the target pixel in is the pixel value of the surroundings, the target pixel is stored as it is, and the condition of 3) 1) is not met. The previous pixel in the traveling direction is the index pixel value,
In the image processing method in which the target pixel is stored as it is, when the next pixel is the peripheral pixel value, the condition of 4) 1) is not met, and it is judged in the sequential type and the scanning line parallel direction Regarding the scanning line one before, the pixel one pixel before the pixel corresponding to the target pixel in the scanning line advancing direction is the index pixel value, and the scanning pixel advancing direction is the target pixel in the scanning pixel one second after. When the pixel after the corresponding pixel is the surrounding pixel value, the target pixel is stored as it is, and the conditions of 5) 1) to 4) are not met, and the determination is performed sequentially, The pixel corresponding to the position of the target pixel on the previous scanning line in the parallel direction of the scanning lines is an index pixel value, and is judged in parallel type,
When the pixels before and after this pixel in the traveling direction of one scanning line have peripheral pixel values, the target pixel is set as an index pixel value,
6) When the conditions of 1) to 4) are not met,
Judging by the sequential type, the pixel immediately before in the traveling direction of one scanning line is an index pixel value, and judged by the parallel type, this pixel in the scanning lines before and after this pixel in the parallel direction of the scanning lines When the pixel corresponding to the position of is the surrounding pixel value, the target pixel is set as the index pixel value, and 7) 1) to 6)
If the condition is not met, the pixel thinning method that sets the target pixel as the surrounding pixel value.