JPH1011589A - Picture processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture processing method of precisely extracting only the outline of a graphic (object) with a simple processing and of precisely calculating the peripheral length of the object. SOLUTION: A picture processing for extracting only the outline M from the picture of the object is executed in the method. The respective picture elements of the picture are binarized with arbitrary brightness and the value and position of the arbitrary binarized picture element are defined as Pij , the values and the positions of four upper/lower/right/left picture elements adjacent to the picture element Pij are defined as Pij-1 , P1-1j , Pi+1j and Pij+1 . Then, the picture element Pij and the adjacent picture elements are processed by Boolean algebra and the processing is executed on all the picture elements. Thus, only the outline M of the object is extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing method for recognizing a shape of an object by a computer.

[0002]

2. Description of the Related Art Conventionally, when extracting an outline as a line that forms the outline of an object from the image of the object, the image of the object is converted into a multi-valued image represented by multi-level values for each degree of brightness. Then, this multi-valued image is differentiated to emphasize only the outline portion (the portion forming the outline) where the change in brightness is large, and image processing is performed to binarize this with an arbitrary brightness threshold, and only the outline is processed. Was extracted.

[0003]

However, since the value of the contour portion emphasized by the differential processing has a width and is not constant, it is difficult to select a threshold value, and thus the width of the extracted contour portion varies. And accurate contours cannot be extracted. Also, since the width of the outline portion of the binarized image is not equal to one pixel, when calculating the circumference length of the object, the circumference length varies depending on which pixel on the outline portion calculates the circumference length. As a result, there has been a problem that the method of calculating the circumference is difficult and accuracy is deteriorated.

Further, in the above method, complicated hardware and software are required for extracting the contour and calculating the perimeter of the object, so that there is a problem that the processing speed is slow and the device price is high.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing method capable of accurately extracting only the contour of a figure (object) by simple processing and accurately calculating the perimeter of the object.

[0006]

According to a first aspect of the present invention, there is provided an image processing method for extracting an outline of an object from an image of the object. The value and position of the binarized arbitrary pixel are defined as P _ij, and the values and positions of the four pixels vertically, horizontally, and horizontally adjacent to the pixel P _ij are defined as P _ij−1 , P _i−1j and P _{i, respectively. + 1j} , P
_{ij + 1} , and the pixel P _ij and each of the adjacent pixels are

[0007]

(Equation 1)

The processing is performed by the Boolean algebra represented by the above equation, and this processing is performed for all pixels to extract the contour of the object.

According to a second aspect of the present invention, in the image processing method for extracting an outline from an image of an object, each pixel of the image is binarized at an arbitrary brightness, and a value of the binarized arbitrary pixel is determined. _Let P _{ij be} the position, and the values and positions of the eight pixels up, down, left, and right in the vicinity of the pixel P _ij are P _i-1j-1 , P _ij-1 , P
_{i + 1j-1, P i} -1j, P i + 1j, P i-1j + 1, P ij + 1, P i + 1j +1
And the pixel P _ij and each of the pixels in the vicinity thereof are

[0010]

(Equation 3)

The processing is carried out by the Boolean algebra represented by the above formula, and this processing is performed for all the pixels to extract the contour of the object.

That is, the gist of the present invention is that first, a threshold value is set between the brightness of an object and the brightness of the background, the image of the object is binarized, and the value of a pixel forming an outline of the obtained binary image is obtained. Is an image processing which can extract an accurate contour of an object only by processing the above binary image by the logical operation formula of Expression 1 so that the value of the pixel in the other part becomes "1" and the value of the pixel in the other part becomes "0". The point is that the method was invented. By performing such processing, it is possible to extract a contour in which the width of the contour portion is equal to one pixel, and to obtain the perimeter of a figure (object) by calculating the sum of the values of the pixels forming the contour. Can be.

[0013]

Next, an image processing method according to the present invention will be described with reference to the accompanying drawings.

First, an object is captured in an image in order to recognize the shape of the object using a scanner, a CCD camera, or the like. This image is binarized by setting a threshold of brightness between the brightness of the object surface and the brightness of the background portion, for example, with an arbitrary brightness threshold that can distinguish the object and the background portion, thereby forming a binary image. obtain. This binary image is shown in FIG.

As shown in FIG. 4, the binary image 30 is m × n
Pixels at any position (i, j)
The pixel P _ij 10 of (1 ≦ i ≦ n, 1 ≦ j ≦ m) has the density value P
("1" or "0").

Next, the pixels constituting the binary image 30 are
FIG. 3 shows the values represented by the values of each pixel.

In the figure, the pixels in the white portions are "0", and the pixels in the hatched portions are "1".

As shown in the binary image 30 of FIG. 3, the contour of the object is at the boundary between "0" and "1". If "1" in contact with "0" is extracted, the contour is obtained.

Next, a process of extracting the contour of the binary image 30 is performed.

Any position (i, j) (1 ≦ i ≦ n, 1 ≦
When processing the pixel P _ij 10 of (j ≦ m), the values and positions of the four pixels above, below, left, and right adjacent to the pixel P _ij 10 are respectively represented by P _ij-1 , P _i-1j , P _{i + 1j} , P _{ij + 1} ,

[0021]

(Equation 1)

The processing is performed by the Boolean algebra represented by FIG. 2 shows the binary image thus processed.

As shown in FIG. 2, the pixel P _ij 10 is P ′ _ij
20, pixel P _i-1j 12 is P ′ _i-1j 22, pixel P _i-1j-1 1
4 has been converted to P ' _i-1j-1 24.

That is, the pixel P _ij 10 has a value of “1”, the pixel P _i-1j 12 has a value of “1”, and the pixel P _i-1j-1 14 constituting the background has a value of “0”. By substituting these values and the values of the four pixels above, below, left and right into the Boolean algebra of Equation 1, the pixel P _ij 10 becomes “0”,
The pixel _Pi-1j- 12 is "1", and the pixel _Pi-1j-1 14 is "0".
Respectively. FIG. 1 is a diagram showing the pixels constituting the binary image 30 processed in this way, with the values of the respective pixels.

In the figure, the pixels in the white portions are "0", and the pixels in the hatched portions are "1".

As shown in FIG. 1, the pixel _P'ij 20 is "0", the pixel _P'i-1j 22 is "1", also pixel P'
_i-1j-1 24 is converted to a value of "0", that is, only the pixels forming the contour M of the object among the pixels constituting the processed binary image 40 are converted to "1". Can be extracted.

In other words, a pixel forming the outline M of the figure has a value of “1”, and at least one of the pixels adjacent to the pixel has a value of “0”. is there. So Boolean algebra

[0028]

(Equation 1)

In the above,

[0030]

(Equation 2)

The condition that the operation result of the part is "0" is as follows.
_{Each of the} elements P _ij-1 , P _i-1j , P _{i + 1j} , and P _{ij +1} is “1”
And the condition that the operation result is “1” is based on the element P
This is a case where at least one of _{ij −1} , P _i−1j , P _{i + 1j} , and P _{ij + 1} is “0”. Therefore, the pixel P ′ _ij 20 is “1”
Is that the value of the portion of Equation 2 is “1” and the pixel P
_This is the case when the value of _ij10 is "1". This satisfies the above-described condition for forming a pixel forming the contour M, and when this condition is not satisfied, the value is “0”, so that only the contour M of the object can be extracted.

The contour M of the object thus extracted is
Since the width is formed by one pixel, the width of the outline M portion after binarization has no variation and is accurate. Also, since the width of the outline M is formed by one pixel,
By calculating the sum of the values of the pixels forming the contour M,
The perimeter of the object can be calculated.

As described above, the brightness threshold between the brightness of the object surface and the brightness of the background portion is set, the image of the object is binarized, and the contour M of the obtained binary image is formed. Only the outline M of the figure (object) is extracted by simply processing the binary image with the logical operation formula of Equation 1 so that the pixel value is “1” and the pixel values of the other parts are “0”. Can,
In addition, by calculating the sum of the values of the pixels forming the contour M, the exact perimeter of the figure (object) can be obtained.

After binarizing the captured image, the value and position of an arbitrary pixel are represented by P _ij , and the values and positions of eight pixels in the vicinity of the pixel are represented by P _i-1j-1 , respectively. P _ij-1 , P
_{i + 1j-1, P i} -1j, P i + 1j, P i-1j + 1, P ij + 1, P i + 1j + 1
And the arbitrary pixel P _ij and the eight pixels up, down, left, and right in the vicinity thereof

[0035]

(Equation 3)

By performing processing using a Boolean algebra expressed as follows and performing this processing for all pixels, it is possible to more accurately extract only the outline of the figure and obtain the perimeter of the figure.

[0037]

In summary, according to the present invention, since image processing for extracting only the contour of an object can be performed only by a simple logical operation, computer processing by complicated software is not required, and the processing speed is increased. In addition, since the outline is extracted after directly binarizing the captured image, the width of the extracted outline portion is formed by one pixel, so that the object can be easily and accurately calculated from the sum of the values of the pixels forming the outline. The perimeter can be determined.

Further, since the present invention can be easily performed even by hardware processing by a logic circuit, high-speed processing can be performed and an inexpensive image processing apparatus can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a binary image processed by the method of the present invention.

FIG. 2 is a diagram showing a binary image processed by the method of the present invention.

FIG. 3 is a diagram illustrating a general binary image.

FIG. 4 is a diagram showing a general binary image.

[Explanation of symbols]

M contour 10 pixel P _ij 12 pixel P _i-1j 14 pixel P _i-1j-1 20 pixel P ′ _ij 22 pixel P ′ _i-1j 24 pixel P ′ _i-1j-1 30 binary image 40 binary image

Claims (2)

[Claims] In an image processing method for extracting an outline from an image of an object, each pixel of the image is binarized at an arbitrary brightness, and a value and a position of the binarized arbitrary pixel are represented by P
and _ij, and the position and the value of vertical and horizontal 4 pixels adjacent to the pixel _{P ij P ij-1, P} i-1j , respectively, P i _{+ 1j,} and P _{ij + 1,} the adjacent to the pixel P _ij Each pixel is expressed as An image processing method characterized by processing using a Boolean algebra represented by (1) and performing this processing on all pixels to extract the contour of the object. 2. An image processing method for extracting an outline from an image of an object, wherein each pixel of the image is binarized at an arbitrary brightness, and a value and a position of the binarized arbitrary pixel are represented by P
_ij, and the values and positions of eight pixels in the vicinity of the pixel P _ij are represented by P _i-1j-1 , P _ij-1 , P _{i + 1j-1} , P _i-1j , respectively.
P _{i + 1j} , P _{i-1j + 1} , P _{ij + 1} , P _{i + 1j +1} and the pixel P
_ij and each of the above pixels in the vicinity thereof are An image processing method characterized by processing using a Boolean algebra represented by (1) and performing this processing on all pixels to extract the contour of the object.