JP4156469B2 - Edge detection apparatus and method, profile determination apparatus and method, and program - Google Patents

Description

  The present invention relates to an edge detection apparatus and method for detecting edges existing between pixels constituting an image, and a profile for determining a profile shape of pixel values constituting an image, for example, when enlarging or reducing an image represented by image data The present invention relates to a determination apparatus and method, a program for causing a computer to execute an edge detection method and a profile determination method.

  Conventionally, image data obtained by photoelectrically reading an image recorded on a photographic film or image data obtained by imaging a subject with an imaging device such as a digital camera or a camera-equipped mobile phone is used as the image data. Enlargement and reduction are performed to fit the size of the monitor to be reproduced. In particular, when sending image data obtained by taking an image of a subject with a camera-equipped mobile phone as an e-mail, a service is also provided that scales the image data according to the size of the liquid crystal monitor of the destination mobile phone. ing.

  Such enlargement / reduction of the image data is performed by interpolating new pixels according to the enlargement ratio between the pixels constituting the image represented by the image data. As methods for interpolating new pixels in this manner, various methods such as a linear interpolation method, a nearest neighbor method, a bilinear method, and a bicubic method are known.

  However, when the image data is enlarged / reduced using only a single method, there is a problem that blur or shaggy occurs in an edge portion included in the image. For this reason, a method has been proposed in which an edge component included in an image is detected and an interpolation operation is performed by different processing between the edge portion and the non-edge portion (see Patent Document 1).

In order to detect an edge from an image in the method described in Patent Document 1, a Sobel filter or a Laplacian filter is generally used. Such a Sobel filter or Laplacian filter has an odd number of taps of the shortest 3 taps, and can detect an edge by determining whether or not the pixel of interest is an edge by filtering.
JP 2002-312020 A

  By the way, when enlarging or reducing an image, since a new pixel is interpolated between pixels, it is necessary to determine whether or not there is an edge between pixels instead of the pixels included in the image. However, when an edge is detected using the above-described filter having an odd number of taps, it is only possible to determine whether the pixel of interest in the image itself is an edge, and whether an edge exists between pixels. It cannot be judged.

  The present invention has been made in view of the above circumstances, and an object thereof is to be able to detect an edge existing between pixels constituting an image.

  Another object of the present invention is to make it possible to determine a profile shape of pixel values constituting an image.

A first edge detection apparatus according to the present invention includes a filtering unit that performs a filtering process using a difference filter on two adjacent pixels on an image to obtain a difference between pixel values of the two adjacent pixels;
Determination means for determining whether or not the absolute value of the difference is equal to or greater than a predetermined threshold value, and determining that an edge exists between the two adjacent pixels when the determination is positive. It is characterized by that.

  The “difference filter” includes not only a filter for obtaining a simple difference between two adjacent pixels but also a filter capable of obtaining a weighted difference. Specifically, a filter with an even number of taps, for example, a 2-tap filter with a filter value of (−1, 1) can be used.

The second edge detection apparatus according to the present invention performs a filtering process using a difference filter on each of three pixel pairs including two adjacent pixels included in four pixels adjacent in series on the image, and performs the process described above. Three primary differences are obtained for each of the pixel values of one pixel pair, and the filtering process by the difference filter is applied to each of the two adjacent primary difference pairs in the three primary differences to obtain two secondary Filtering means for obtaining a difference;
Detection means for detecting whether or not an edge exists between two central pixels of the four pixels adjacent in series based on a positive / negative relationship between the three primary differences and the two secondary differences It is characterized by comprising.

The third edge detection apparatus according to the present invention performs a filtering process using a difference filter on each of three pixel pairs including two adjacent pixels included in four pixels adjacent in series on the image, and performs the process described above. Three primary differences are obtained for each of the pixel values of one pixel pair, and the filtering process by the difference filter is applied to each of the two adjacent primary difference pairs in the three primary differences to obtain two secondary First filtering means for obtaining a difference;
Second filtering means for performing a filtering process by the difference filter on the two central pixels of the four pixels adjacent in series to obtain a difference between pixel values of the two central pixels;
Based on the positive / negative relationship between the three primary differences and the two secondary differences and the determination result of whether or not the absolute value of the difference between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value. And detecting means for detecting whether or not an edge exists between the two central pixels.

The first profile determination device according to the present invention performs a filtering process using a difference filter on three pixel pairs including two adjacent pixels included in four pixels adjacent in series in the pixels on the image. Then, three primary differences are obtained for each of the pixel values of the three pixel pairs, and two adjacent primary difference pairs in the three primary differences are filtered by the difference filter, respectively. Filtering means for obtaining two secondary differences;
And determining means for determining profile shapes of pixel values in the vicinity of the four pixels adjacent in series based on a positive / negative relationship between the three primary differences and the two secondary differences. Is.

The second profile determination device according to the present invention performs a filtering process using a difference filter on three pixel pairs including two adjacent pixels included in four pixels adjacent in series in the pixels on the image. Then, three primary differences are obtained for each of the pixel values of the three pixel pairs, and two adjacent primary difference pairs in the three primary differences are filtered by the difference filter, respectively. First filtering means for obtaining two secondary differences;
Second filtering means for obtaining a difference between pixel values of the two central pixels by performing a filtering process using a differential filter on the two central pixels of the four pixels adjacent in series;
Based on the positive / negative relationship between the three primary differences and the two secondary differences and the determination result of whether or not the absolute value of the difference between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value. And profile determination means for determining profile shapes of pixel values in the vicinity of the four pixels adjacent in series.

A first edge detection method according to the present invention obtains a difference between pixel values of two adjacent pixels by performing a filtering process using a difference filter on two adjacent pixels on an image,
It is determined whether or not the absolute value of the difference is equal to or greater than a predetermined threshold value, and when the determination is affirmative, it is determined that an edge exists between the two adjacent pixels. Is.

In the second edge detection method according to the present invention, a filtering process using a difference filter is performed on each of three pixel pairs including two pixels adjacent to each other included in four pixels adjacent in series on the image. Three primary differences are obtained for each of the pixel values of one pixel pair, and the filtering process by the difference filter is applied to each of the two adjacent primary difference pairs in the three primary differences to obtain two secondary Get the difference
Based on the positive / negative relationship between the three primary differences and the two secondary differences, it is detected whether an edge exists between the two central pixels of the four pixels adjacent in series. It is a feature.

In the third edge detection method according to the present invention, the three pixel pairs formed by two adjacent pixels included in the four pixels adjacent in series on the image are each subjected to a filtering process using a difference filter, and the 3 Three primary differences are obtained for each of the pixel values of one pixel pair, and the filtering process by the difference filter is applied to each of the two adjacent primary difference pairs in the three primary differences to obtain two secondary Get the difference
Applying a filtering process by the difference filter to the center two pixels of the four pixels adjacent in series to obtain a difference between pixel values of the center two pixels,
Based on the positive / negative relationship between the three primary differences and the two secondary differences and the determination result of whether or not the absolute value of the difference between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value. , Detecting whether or not an edge exists between the two central pixels.

In the first profile determination method according to the present invention, a filtering process using a differential filter is performed on three pixel pairs each including two adjacent pixels included in four pixels adjacent in series in a pixel on an image. Then, three primary differences are obtained for each of the pixel values of the three pixel pairs, and two adjacent primary difference pairs in the three primary differences are filtered by the difference filter, respectively. Obtain two secondary differences,
A profile shape of pixel values in the vicinity of the four pixels adjacent in series is determined based on a positive / negative relationship between the three primary differences and the two secondary differences.

In the second profile determination method according to the present invention, a filtering process using a difference filter is performed on each of three pixel pairs including two adjacent pixels included in four pixels adjacent in series. Then, three primary differences are obtained for each of the pixel values of the three pixel pairs, and two adjacent primary difference pairs in the three primary differences are filtered by the difference filter, respectively. Obtain two secondary differences,
Applying a filtering process using a difference filter to the center two pixels of the four pixels adjacent in series to obtain a difference between pixel values of the center two pixels,
Based on the positive / negative relationship between the three primary differences and the two secondary differences and the determination result of whether or not the absolute value of the difference between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value. The profile shape of the pixel values in the vicinity of the four pixels adjacent in series is determined.

  The edge detection method and profile determination method according to the present invention may be provided as a program for causing a computer to execute the method.

  According to the first edge detection apparatus and method of the present invention, a filtering process using a difference filter is performed on two adjacent pixels on an image to obtain a difference between pixel values of the two pixels. It is determined whether the absolute value is greater than or equal to a predetermined threshold value. Here, when the absolute value of the difference between the pixel values of two adjacent pixels is large, it can be considered that an edge exists there. Therefore, by determining whether or not the absolute value of the difference is greater than or equal to a predetermined threshold value, it is possible to detect whether or not there is an edge between pixels instead of on the pixels of the image. Further, since only the difference is calculated, it is possible to detect whether an edge exists at high speed by a simple calculation.

  According to the second edge detection apparatus and method of the present invention, the filtering process by the difference filter is performed on each of the three pixel pairs including the two adjacent pixels included in the four pixels adjacent in series on the image. As a result, three primary differences are obtained for each of the pixel values of the three pixel pairs. Further, filtering processing using a difference filter is performed on two adjacent primary difference pairs in the three primary differences to obtain two secondary differences. Here, the profile of the pixel values of four pixels adjacent in series can be classified according to the positive and negative values of the three primary differences and the two secondary differences, and the three primary differences and the two secondary differences can be classified. If a positive / negative relationship is seen, it can be determined whether or not an edge exists between two central pixels of four pixels adjacent in series. Therefore, based on the positive / negative relationship between the three primary differences and the two secondary differences, by detecting whether there is an edge between the two central pixels of the four pixels adjacent in series, It is possible to detect whether there is an edge between pixels, not on the pixels of the image. Further, since only the difference is calculated, it is possible to detect whether an edge exists at high speed by a simple calculation.

  According to the third edge detection apparatus and method of the present invention, the filtering process by the difference filter is performed on each of the three pixel pairs including the two adjacent pixels included in the four pixels adjacent in series on the image. As a result, three primary differences are obtained for each of the pixel values of the three pixel pairs. Further, filtering processing using a difference filter is performed on two adjacent primary difference pairs in the three primary differences to obtain two secondary differences. Further, a filtering process using a difference filter is performed on two central pixels among four pixels adjacent in series to obtain a difference between pixel values of the two central pixels. Here, the profiles of four pixel values adjacent in series can be classified according to the positive and negative values of the three primary differences and the two secondary differences, and the positive and negative values of the three primary differences and the two secondary differences can be classified. From the relationship, it can be determined whether or not an edge exists between the two central pixels of four pixels adjacent in series. Also, when it is determined that an edge exists, if the absolute value of the difference between the pixel values of the two central pixels is small, the probability that the edge exists there is small, but if the absolute value of the difference is large, It can be assumed that there is a true edge there. Therefore, based on the positive / negative relationship between the three primary differences and the two secondary differences and the determination result of whether or not the absolute value of the difference between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value, By detecting whether there is an edge between two pixels in the middle of four pixels adjacent in series, it is ensured that there is an edge between the pixels, not on the pixel of the image Can be detected. Further, since only the difference is calculated, it is possible to detect whether an edge exists at high speed by a simple calculation.

  According to the first profile determination apparatus and method of the present invention, the filtering process by the difference filter is performed on each of the three pixel pairs including the two adjacent pixels included in the four pixels adjacent in series on the image. As a result, three primary differences are obtained for each of the pixel values of the three pixel pairs. Further, filtering processing using a difference filter is performed on two adjacent primary difference pairs in the three primary differences to obtain two secondary differences. Here, the profile shapes of four pixel values adjacent in series can be classified according to the positive and negative values of the three primary differences and the two secondary differences, and the positive and negative of the three primary differences and the two secondary differences can be classified. From this relationship, it is possible to determine what shape the profile shape of the four pixel values adjacent in series is as an edge or not as an edge. Therefore, by determining the profile shape of four neighboring pixels in series based on the positive / negative relationship between the three primary differences and the two secondary differences, whether the four pixel neighborhoods are edges or not edges Or the like.

  According to the second profile determination apparatus and method of the present invention, the filtering process by the difference filter is performed on each of the three pixel pairs including the two adjacent pixels included in the four pixels adjacent in series on the image. As a result, three primary differences are obtained for each of the pixel values of the three pixel pairs. Further, filtering processing using a difference filter is performed on two adjacent primary difference pairs in the three primary differences to obtain two secondary differences. In addition, a filtering process using a difference filter is performed on two central pixels of four pixels adjacent in series to obtain a difference between pixel values of the two central pixels. Here, the profile shapes of four pixel values adjacent in series can be classified according to the positive and negative values of the three primary differences and the two secondary differences, and the positive and negative of the three primary differences and the two secondary differences can be classified. From this relationship, it is possible to determine what shape the profile shape of the four pixel values adjacent in series is as an edge or not as an edge. When the profile shape is determined to be an edge and the absolute value of the difference between the pixel values of the two central pixels is small, the probability that an edge exists there is small, but the absolute value of the difference is large. In this case, the profile shape can be regarded as a true edge because a true edge exists there. Therefore, based on the positive / negative relationship between the three primary differences and the two secondary differences and the determination result of whether or not the absolute value of the difference between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value, By determining the profile shape in the vicinity of four pixels adjacent in series, it can be reliably determined whether the vicinity of the four pixels is an edge or not.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic block diagram showing the configuration of an image enlargement / reduction apparatus to which an edge detection apparatus according to a first embodiment of the present invention is applied. As shown in FIG. 1, the image enlargement / reduction apparatus according to the first embodiment of the present invention includes an input unit 1, a filtering unit 2, a determination unit 3, an interpolation unit that receives input of image data S0 and an enlargement factor K of the image data S0. An interpolation calculation unit 4 that calculates a pixel value of a pixel, and a control unit 5 that controls operations of the input unit 1, the filtering unit 2, the determination unit 3, and the interpolation calculation unit 4 are provided.

  Here, the image represented by the image data S0 (hereinafter, the reference symbol S0 is also used for the image) is composed of two-dimensionally arranged pixels as shown in FIG. In this embodiment and other embodiments described later, the x direction and the y direction are defined as shown in FIG.

  The filtering unit 2 uses a difference filter for two adjacent pixels between which pixels to be interpolated by enlargement (hereinafter referred to as interpolation pixels P) are located in each row in the x direction and the y direction of the image S0. A filtering process is performed to calculate the difference d0 between the pixel values of the two pixels. FIG. 3 is a diagram illustrating an example of the difference filter. As shown in FIG. 3, the difference filter used in the filtering unit 2 of the first embodiment is a 2-tap filter having a filter value of (−1, 1). Note that the difference filter is not limited to this, and a filter having a filter value for obtaining a weighted difference between two pixel values or a filter having an even number of taps of two or more taps may be used.

  The determination unit 3 determines whether or not the absolute value of the difference d0 is greater than or equal to a predetermined threshold value Th1, and if this determination is affirmative, an edge exists between two adjacent pixels that have obtained the difference d0. Then, it is determined, and the determination result is output to the interpolation calculation unit 4.

  Based on the determination result of the determination unit 3, the interpolation calculation unit 4 determines whether the interval between two adjacent pixels between which the interpolation pixel P is located is an edge or not. The pixel value of the interpolated pixel P is calculated by different calculations. Specifically, when it is determined that the pixel is not an edge, the pixel value of the interpolation pixel P is calculated using the bicubic method.

  Here, the bicubic method is a method of cubic interpolation, and is a method of obtaining the pixel value of the interpolation pixel P using 16 pixels in the vicinity of the interpolation pixel P. Hereinafter, the bicubic method will be described.

FIG. 4 is a diagram for explaining the bicubic method. As shown in FIG. 4, when the point P is set as the position of the interpolation pixel P, a pixel indicated by a black circle in FIG. 4 is referred to as a primary neighborhood, and a pixel indicated by a white circle is referred to as a secondary neighborhood. For each of the first-order neighborhood and the second-order neighborhood, as shown in the following equation (1), the distances dx and dy (simply indicated as d in the equation (1)) independently in the x direction and the y direction, respectively. The weights Wx and Wy are obtained, and finally the weight W = WxWy for the pixel is obtained.

For example, when the weights Wx, Wy, and W are obtained for the pixel (second order neighborhood) of (−1, −1) in FIG.

It becomes.

When W (i, j) is the weight of the pixel (i, j) and f (i, j) is the pixel value of the pixel (i, j), the pixel value f ′ (P) of the interpolation pixel P is

Can be calculated.

  In the first embodiment and other embodiments described later, the pixel value of the interpolation pixel P is calculated by applying the bicubic method only in the one-dimensional direction of the x direction or the y direction.

  On the other hand, for the portion determined to be an edge, the pixel value of the interpolation pixel P is obtained as follows. FIG. 5 is a diagram illustrating a profile of pixel values for a portion determined to be an edge. In FIG. 5, the horizontal direction is the direction in which the pixels are arranged, and the vertical direction is the direction in which the magnitude of the pixel value is indicated. When it is determined that an edge exists between two adjacent pixels G2 and G3, two pixels G1 to G4 adjacent in series obtained by adding two adjacent pixels G1 and G4 to the two pixels, respectively. The value profile is as shown in FIG. 5 (a) or FIG. 5 (b).

  When the profile has the step edge shape shown in FIG. 5A, a middle line M (see the alternate long and short dash line) that bisects the distance between the pixels G2 and G3 in the direction in which the pixels are arranged is defined. When an interpolation pixel (referred to as P1) exists, the value on the extension line of the straight line connecting the pixels G3 and G4 is set as the pixel value of the interpolation pixel P1. When an interpolation pixel (P2) exists on the left side of the middle line M, the value on the extension line of the straight line connecting the pixels G1 and G2 is set as the pixel value of the interpolation pixel P2.

  When the profile has the edge shape shown in FIG. 5B, an intersection C between a straight line extension line connecting the pixels G1 and G2 and a straight line extension line connecting the pixels G3 and G4 is obtained. If the interpolation pixel P1 exists on the right side of the intersection C, the value on the extension line of the straight line connecting the pixels G3 and G4 is set as the pixel value of the interpolation pixel P1. When the interpolation pixel P2 exists on the left side of the intersection C, the value on the extension line of the straight line connecting the pixels G1 and G2 is set as the pixel value of the interpolation pixel P2.

  Here, the pixel value of the interpolation pixel P is calculated using only the pixel values of two pixels, but the pixel values of three or more pixels may be used. In this case, it may be difficult to connect the pixels with a straight line. For this reason, the pixels may be connected by a curve defined by an arbitrary function such as a spline curve, and the value on the extension line of the curve may be the value of the interpolation pixel P.

  Here, in the following description, the calculation when it is determined to be an edge is referred to as a first interpolation calculation, and the calculation when it is determined not to be an edge is referred to as a second interpolation calculation.

  Next, processing performed in the first embodiment will be described. FIG. 6 is a flowchart showing processing performed in the first embodiment. In the present embodiment, it is assumed that the interpolation pixel P exists between the pixels of the image S0. First, the input unit 1 accepts input of the image data S0 to be enlarged and the enlargement factor K of the image data S0 (step S1). The direction for interpolating the pixels is first set in the x direction (step S2). Next, for the first interpolation pixel P corresponding to the enlargement factor K (for example, an image represented by the enlarged image data S1 (the pixel located in the upper left corner of the image hereinafter also using the reference symbol S1)), a filtering unit 2 calculates a difference d0 by applying a filtering process using a difference filter to two adjacent pixels between which the interpolated pixel P is located (step S3).

  And the determination part 3 determines whether the absolute value of the difference d0 is more than threshold value Th1 (step S4). If step S4 is affirmed, the interpolation calculation unit 4 calculates the pixel value of the interpolation pixel P by the first interpolation calculation, assuming that an edge exists between two adjacent pixels for which the difference d0 has been obtained ( Step S5). On the other hand, if step S4 is negative, the interpolation calculation unit 4 calculates the pixel value of the interpolation pixel P by the second interpolation calculation, assuming that no edge exists between the two adjacent pixels for which the difference d0 is obtained. (Step S6).

  Then, the control unit 5 determines whether or not the pixel values have been calculated for all the interpolation pixels P (step S7). If step S7 is negative, the interpolation pixel P for calculating the pixel value is changed to the next interpolation pixel P. (Step S8), and the process returns to step S3.

  If step S7 is affirmed, it is determined whether or not pixel values have been calculated for all interpolation pixels P in the y direction (step S9). If step S9 is negative, the interpolation direction is set to the y direction (step S10), and the process returns to step S3. When step S9 is affirmed, the enlarged image data S1 including the interpolation pixel P is output (step S11), and the process is terminated.

  As described above, in the first embodiment, when the absolute value of the difference d0 between two adjacent pixels on the image is greater than or equal to the threshold Th, it is considered that an edge exists there. It is possible to detect whether there is an edge between pixels, not on the pixels of the image S0. Further, since only the difference d0 is calculated, it is possible to detect whether or not an edge exists at high speed by a simple calculation.

  Next, a second embodiment of the present invention will be described. FIG. 7 is a schematic block diagram showing a configuration of an image enlargement / reduction apparatus to which the edge detection apparatus according to the second embodiment of the present invention is applied. As shown in FIG. 7, the image enlargement / reduction apparatus according to the second embodiment of the present invention includes an input unit 11, a filtering unit 12, a determination unit 13, and an interpolation that receive input of image data S0 and an enlargement factor K of the image data S0. An interpolation calculation unit 14 that calculates the pixel value of the pixel P, and a control unit 15 that controls operations of the input unit 11, the filtering unit 12, the determination unit 13, and the interpolation calculation unit 14 are provided.

  The filtering unit 12 performs a filtering process as follows. FIG. 8 is a diagram for explaining a filtering process performed in the filtering unit 12 according to the second embodiment. The filtering unit 12 is adjacent to each of two adjacent pixels G2 and G3 between which the interpolation pixel P is located and each of the two pixels G2 and G3 for each column in the x direction and the y direction of the image S0. For four pixels G1 to G4 that are adjacent to each other in series, each consisting of two pixels G1 and G4, a diagram is shown for three pixel pairs G1 and G2, pixel pairs G2 and G3, and pixel pairs G3 and G4 each consisting of two adjacent pixels. The difference filter of the pixel value of pixel pair G1, G2, pixel pair G2, G3, and pixel pair G3, G4 is calculated as primary difference d1, d2, d3 by performing the filtering process by the difference filter shown in FIG.

  Subsequently, the filtering unit 12 similarly performs a filtering process using a difference filter on two adjacent primary difference pairs d1, d2 and primary difference pairs d2, d3 in the three primary differences d1, d2, d3. The difference between the primary difference pairs d1, d2 and d2, d3 is calculated as secondary differences d4, d5.

  The determination unit 13 determines whether an edge exists between two adjacent pixels G2 and G3 based on the positive / negative relationship between the primary differences d1, d2, and d3 and the secondary differences d4 and d5, The determination result is output to the interpolation calculation unit 14.

  9 to 11 are tables showing the relationship between the positive / negative of the primary differences d1, d2, d3 and the secondary differences d4, d5 of the four pixels adjacent in series and the profile shape of the four pixels adjacent in series. It is. There are a total of 18 combinations of positive and negative of the primary differences d1, d2, d3 and the secondary differences d4, d5 of four pixels adjacent in series. There are two combinations of edge 1 and edge 2 shown in FIG. 9 in which an edge exists between two adjacent pixels G2 and G3. The edge 1 corresponds to FIG. 5A in the first embodiment, and a right rising edge and (d1, d2, d3, d4, d5) = (+, +, +, +, −) and There are two types of left rising edges where (d1, d2, d3, d4, d5) = (−, −, −, −, +). The edge 2 corresponds to FIG. 5B in the first embodiment, and is convex downward such that (d1, d2, d3, d4, d5) = (+, +, +, +, +). Upwardly rising edge where (d1, d2, d3, d4, d5) = (+, +, +, −, −), (d1, d2, d3, d4, d5) = ( Downward convex left rising edge that becomes −, −, −, +, +), and upward convex leftward that becomes (d1, d2, d3, d4, d5) = (−, −, −, −, −) There are four types of rising edges.

  The determination unit 13 stores the tables shown in FIGS. 9 to 11, and the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5 of four pixels adjacent in series is shown in FIG. When the relationship between the edge 1 and the edge 2 shown in FIG. 2 is established, it is determined that an edge exists between two adjacent pixels G2 and G3. Further, when the positive / negative relationship of the primary differences d1, d2, d3 and the secondary differences d4, d5 of the four pixels adjacent in series is the peak, valley, and other relationships shown in FIGS. 10 and 11, It is determined that no edge exists between two adjacent pixels G2 and G3.

  Similar to the interpolation calculation unit 4 in the first embodiment, the interpolation calculation unit 14 performs the first interpolation calculation when it is determined that an edge is between two adjacent pixels between which the interpolation pixel P is located. When it is determined that the pixel is not an edge, the second interpolation calculation is performed to calculate the pixel value of the interpolation pixel P.

  Next, processing performed in the second embodiment will be described. FIG. 12 is a flowchart showing processing performed in the second embodiment. In the second embodiment, it is assumed that the interpolation pixel P exists between the pixels of the image S0 as in the first embodiment. First, the input unit 11 receives input of the image data S0 to be enlarged and the enlargement factor K of the image data S0 (step S21). The direction for interpolating the pixels is first set in the x direction (step S22). Next, for the first interpolation pixel P corresponding to the enlargement factor K (for example, the pixel located in the upper left of the image S1), the filtering unit 12 starts from the four pixels G1 to G4 adjacent in series where the interpolation pixel P is located. The primary differences d1, d2, d3 and the secondary differences d4, d5 are calculated (step S23).

  Then, based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, the determination unit 13 has an edge between two adjacent pixels G2, G3 between which the interpolation pixel P is located. It is determined whether or not it exists (step S24). If step S24 is positive, the interpolation calculation unit 14 calculates the pixel value of the interpolation pixel P by the first interpolation calculation based on the determination result of the determination unit 13 (step S25). On the other hand, if step S24 is negative, the interpolation calculation unit 14 calculates the pixel value of the interpolation pixel P by the second interpolation calculation based on the determination result of the determination unit 13 (step S26).

  Then, the control unit 15 determines whether or not the pixel values have been calculated for all the interpolation pixels P (step S27). If step S27 is negative, the interpolation pixel P for calculating the pixel value is changed to the next interpolation pixel P. (Step S28), and the process returns to step S23.

  If step S27 is affirmed, it is determined whether or not pixel values have been calculated for all interpolation pixels P in the y direction (step S29). If step S29 is negative, the interpolation direction is set to the y direction (step S30), and the process returns to step S23. When step S29 is affirmed, the enlarged image data S1 including the interpolation pixel P is output (step S31), and the process is terminated.

  As described above, in the second embodiment, based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, two adjacent pixels G2, G3 between which the interpolation pixel P is located. Since it is determined whether or not there is an edge between them, it is possible to detect whether or not there is an edge between pixels instead of on the pixel of the image S0. Further, since only the differences d1, d2, d3, d4, and d5 are calculated, it is possible to detect whether or not an edge exists at high speed by a simple calculation.

  Next, a third embodiment of the present invention will be described. FIG. 13 is a schematic block diagram showing a configuration of an image enlargement / reduction apparatus to which an edge detection apparatus according to the third embodiment of the present invention is applied. As shown in FIG. 13, the image enlargement / reduction apparatus according to the third embodiment of the present invention includes an input unit 21 that receives input of the image data S0 and the enlargement factor K of the image data S0, and the first and second filtering units 22A. , 22B, the determination unit 23, the interpolation calculation unit 24 that calculates the pixel value of the interpolation pixel P, and the operations of the input unit 21, the first and second filtering units 22A and 22B, the determination unit 23, and the interpolation calculation unit 24 are controlled. The control unit 25 is provided.

  In the same manner as the filtering unit 12 in the second embodiment, the first filtering unit 22A has two adjacent pixels G2 and G3 between which the interpolation pixel P is located and two adjacent to the two pixels. Filtering processing is performed on four pixels G1 to G4 that are adjacent in series, each consisting of two pixels G1 and G4, to calculate primary differences d1, d2, and d3 and secondary differences d4 and d5.

  The second filtering unit 22B performs the filtering process on the two central pixels G2 and G3 of the four pixels G1 to G4 adjacent in series in the same manner as the filtering unit 2 in the first embodiment. A difference d0 (= d2) between pixel values of the pixels G2 and G3 is calculated.

  Similar to the determination unit 13 in the second embodiment, the determination unit 23 is based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5 calculated by the first filtering unit 22A. Then, it is determined whether or not an edge exists between two adjacent pixels G2 and G3 (first determination). That is, when the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5 of the four pixels adjacent in series is the relationship between the edge 1 and the edge 2 shown in FIG. It is determined that an edge exists between the two pixels G2 and G3. Further, when the positive / negative relationship of the primary differences d1, d2, d3 and the secondary differences d4, d5 of the four pixels adjacent in series is the peak, valley, and other relationships shown in FIGS. 10 and 11, It is determined that no edge exists between two adjacent pixels G2 and G3.

  Further, when it is determined that an edge is present, the determination unit 23 determines that the absolute value of the difference d0 between the pixel values of the pixels G2 and G3 is a predetermined threshold Th1, as in the determination unit 3 in the first embodiment. It is determined whether or not this is the case (second determination), and if the second determination is affirmed, it is determined that an edge exists truly. On the other hand, if the second determination is negative, it is determined that there is no edge there. In this way, the second determination is performed even if it is determined in the first determination that an edge is present, for example, as shown in FIG. This is to prevent the noise from being emphasized on the contrary when the interpolation calculation unit 24 performs the first interpolation calculation assuming that the edge is an edge. Then, the determination unit 23 outputs the determination result to the interpolation calculation unit 24.

  Similar to the interpolation calculation unit 4 in the first embodiment, the interpolation calculation unit 24 performs the first interpolation calculation when it is determined that an edge is between two adjacent pixels located between the interpolation pixels P. When it is determined that the pixel is not an edge, the second interpolation calculation is performed to calculate the pixel value of the interpolation pixel P.

  Next, processing performed in the third embodiment will be described. FIG. 15 is a flowchart showing processing performed in the third embodiment. In the third embodiment, it is assumed that the interpolation pixel P exists between the pixels of the image S0 as in the first embodiment. First, the input unit 21 receives input of the image data S0 to be enlarged and the enlargement factor K of the image data S0 (step S41). The direction for interpolating the pixels is first set in the x direction (step S42). Next, for the first interpolation pixel P corresponding to the enlargement factor K (for example, the pixel located in the upper left of the image S1), the first filtering unit 22A has four pixels G1 adjacent in series with the interpolation pixel P positioned therebetween. The primary differences d1, d2, d3 and the secondary differences d4, d5 are calculated from -G4 (step S43). Further, the second filtering unit 22B performs a filtering process using a difference filter on the pixels G2 and G3 to calculate the difference d0 (step S44).

  Then, based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, the determination unit 23 detects an edge between two adjacent pixels G2, G3 between which the interpolation pixel P is located. It is determined whether or not it exists (first determination, step S45). If step S45 is positive, the determination unit 23 determines whether or not the absolute value of the difference d0 is greater than or equal to the threshold value Th1 (second determination, step S46).

  When step S46 is affirmed, the interpolation calculation unit 24 calculates the pixel value of the interpolation pixel P by the first interpolation calculation based on the determination result of the determination unit 23 (step S47). On the other hand, when step S45 and step S46 are denied, the interpolation calculation part 24 calculates the pixel value of the interpolation pixel P by the said 2nd interpolation calculation based on the determination result of the determination part 23 (step S48).

  Then, the control unit 25 determines whether or not the pixel values have been calculated for all the interpolation pixels P (step S49). If step S49 is negative, the interpolation pixel P for calculating the pixel value is changed to the next interpolation pixel P. (Step S50), and the process returns to step S43.

  If step S49 is affirmed, it is determined whether or not pixel values have been calculated for all interpolation pixels P in the y direction (step S51). If step S51 is negative, the interpolation direction is set to the y direction (step S52), and the process returns to step S43. When step S51 is affirmed, the enlarged image data S1 including the interpolation pixel P is output (step S53), and the process is terminated.

  Thus, in the third embodiment, based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, two adjacent pixels G2, G3 between which the interpolation pixel P is located. A first determination is made to determine whether or not an edge exists between the two, and if the first determination is affirmative, the absolute value of the difference d0 between the pixel values of two adjacent pixels G2 and G3 is a threshold. A second determination is made to determine whether or not the value Th is greater than or equal to the value Th, and if the second determination is affirmed, it is assumed that an edge is truly present there. It is possible to reliably detect whether an edge exists between the two. Further, since only the differences d0, d1, d2, d3, d4, and d5 are calculated, it is possible to detect whether or not an edge exists at high speed by a simple calculation.

  Next, a fourth embodiment of the present invention will be described. FIG. 16 is a schematic block diagram showing a configuration of a profile determination device according to the fourth exemplary embodiment of the present invention. As shown in FIG. 16, the profile determination apparatus according to the fourth embodiment of the present invention includes an input unit 31, a filtering unit 32, a determination unit 33, and an input unit 31, a filtering unit 32, and a determination unit that receive input of image data S0. The control part 35 which controls operation | movement of the part 33 is provided.

  In the same manner as the filtering unit 12 in the second embodiment, the filtering unit 32 includes two adjacent pixels G2 and G3 between which the interpolation pixel P is located, and two pixels G1 adjacent to each of the two pixels. , G4, the four adjacent pixels G1 to G4 are subjected to filtering processing to calculate primary differences d1, d2, d3 and secondary differences d4, d5.

  Based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, the determination unit 33 refers to the tables shown in FIGS. It is determined whether the profile shape of the pixel value of G4 is edge 1, edge 2, mountain, valley, or the like, and a determination result R0 is output.

  Note that the determination result R0 is recorded on a recording medium in association with the position of the pixel on the image S0, and when the image S0 is scaled later, the determination result R0 is referred to to determine the first implementation. Similar to the embodiment, different interpolation calculations may be performed on a portion determined to be an edge and a portion determined not to be an edge.

  Next, processing performed in the fourth embodiment will be described. FIG. 17 is a flowchart showing processing performed in the fourth embodiment. First, the input unit 11 receives an input of image data S0 (step S61). The direction for determining the profile shape is first set in the x direction (step S62). Next, with respect to the first pixel for determining the profile shape (for example, the pixel located in the upper left of the image S0), the filtering unit 32 calculates the primary differences d1, d2, d3 from the four adjacent pixels G1 to G4 including the pixel. And secondary differences d4 and d5 are calculated (step S63). Then, based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, the determination unit 33 refers to the tables shown in FIGS. It is determined whether the profile shape is edge 1, edge 2, mountain, valley, or other (step S64), and a determination result R0 is output (step S65).

  Then, the control unit 35 determines whether or not the profile shape has been determined for all the pixels (step S66). If step S66 is negative, the pixel for determining the profile shape is set as the next pixel (step S67). ), The process returns to step S63.

  If step S66 is affirmed, it is determined whether or not the profile shape has been determined for all pixels in the y direction (step S68). If step S68 is negative, the direction for determining the profile shape is set to the y direction (step S69), and the process returns to step S63. If step S68 is positive, the process is terminated.

  As described above, in the fourth embodiment, the profile shapes of four pixels adjacent in series are determined based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5. It can be determined whether the vicinity of four pixels is an edge or not.

  Next, a fifth embodiment of the present invention will be described. FIG. 18 is a schematic block diagram showing a configuration of a profile determination device according to the fifth exemplary embodiment of the present invention. As shown in FIG. 18, the profile determination apparatus according to the fifth embodiment of the present invention includes an input unit 41 that receives input of image data S0, first and second filtering units 42A and 42B, a determination unit 43, and an input. The control part 45 which controls operation | movement of the part 41, 1st and 2nd filtering part 42A, 42B, and the determination part 43 is provided.

  In the same manner as the filtering unit 12 in the second embodiment, the first filtering unit 42A has two adjacent pixels G2 and G3 between which the interpolation pixel P is located and two adjacent to the two pixels. Filtering processing is performed on four pixels G1 to G4 that are adjacent in series, each consisting of two pixels G1 and G4, to calculate primary differences d1, d2, and d3 and secondary differences d4 and d5.

  Similarly to the filtering unit 2 in the first embodiment, the second filtering unit 42B performs a filtering process on the two central pixels G2 and G3 of the four pixels G1 to G4 adjacent in series. A difference d0 between pixel values of the pixels G2 and G3 is calculated.

  Based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, the determination unit 43 refers to the tables shown in FIGS. It is determined whether the profile shape of the pixel value of G4 is any one of edge 1, edge 2, mountain, valley, and others (third determination). Further, when the determination unit 43 determines that the edges 1 and 2 are determined, as in the determination unit 3 in the first embodiment, the absolute value of the difference d0 between the pixel values of the pixels G2 and G3 is a predetermined threshold. It is determined whether or not the value is equal to or greater than the value Th1 (fourth determination). If the fourth determination is affirmed, an edge is truly present there, so that the third determination is correct and adjacent in series. The profile shape of the four pixels to be determined is either edge 1 or edge 2, that is, an edge. On the other hand, if the fourth determination is denied, it is determined that there is no edge there, and the profile shapes of the four pixels adjacent in series are determined to be other.

  Note that the determination result R0 is recorded on a recording medium in association with the position of the pixel on the image S0, and when the image S0 is scaled later, the determination result R0 is referred to to determine the first implementation. Similar to the embodiment, different interpolation calculations may be performed on a portion determined to be an edge and a portion determined not to be an edge.

  Next, processing performed in the fifth embodiment will be described. FIG. 19 is a flowchart showing processing performed in the fifth embodiment. First, the input unit 11 receives an input of image data S0 (step S71). Then, the direction for determining the profile shape is first set in the x direction (step S72). Next, with respect to the first pixel for determining the profile shape (for example, the pixel located in the upper left of the image S0), the filtering unit 32 calculates the primary differences d1, d2, d3 from the four adjacent pixels G1 to G4 including the pixel. And secondary differences d4 and d5 are calculated (step S73). Further, the second filtering unit 42B performs a filtering process using a difference filter on the pixels G2 and G3 to calculate the difference d0 (step S74).

  Then, based on the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5, the determination unit 43 refers to the tables shown in FIGS. It is determined whether the profile shape is edge 1, edge 2, mountain, valley, or other (third determination, step S75). Then, the determination unit 43 determines whether or not the edges 1 and 2 are determined (step S76). If the determination in step S76 is affirmative, whether or not the absolute value of the difference d0 is greater than or equal to the threshold value Th1. Is determined (fourth determination, step S77).

  If the fourth determination is negative, it is determined that there is no edge, and the profile shapes of the four pixels adjacent in series are determined to be other (step S78). If the fourth determination is affirmed, since an edge is truly present there, the determination result R0 is output assuming that the third determination is correct (step S79). In addition, also when step S76 is denied, it progresses to step S79 and outputs determination result R0.

  Then, the control unit 35 determines whether or not the profile shape has been determined for all the pixels (step S80). If step S80 is negative, the pixel for determining the profile is set to the next pixel (step S81). Return to step S73.

  If step S80 is positive, it is determined whether or not the profile shape has been determined for all pixels in the y direction (step S82). If step S82 is negative, the direction for determining the profile shape is set to the y direction (step S83), and the process returns to step S73. If step S82 is positive, the process ends.

  Thus, in the fifth embodiment, the profile shapes of the four pixels G1 to G4 adjacent in series are determined based on the positive / negative relationship of the primary differences d1, d2, d3 and the secondary differences d4, d5. When the third determination is performed and it is further determined that the profile shape is an edge, whether or not the absolute value of the difference d0 between the pixel values of two adjacent pixels G2 and G3 is greater than or equal to the threshold Th Since the fourth determination is performed and if the fourth determination is denied, it is regarded as not an edge. Therefore, it is possible to accurately determine whether the vicinity of the four pixels is an edge or not. it can.

  In the first to third embodiments, when it is determined that the edge is not an edge, the interpolation pixel P is calculated from 16 pixel values (4 pixels in the one-dimensional direction) near the interpolation pixel P using the bicubic method. The pixel value of the interpolation pixel P is calculated from the pixel values of 9 pixels (3 pixels in the one-dimensional direction) or 4 pixels (2 pixels in the one-dimensional direction) in the vicinity of the interpolation pixel P. Also good. Further, although the pixel value of the interpolation pixel P is calculated by one-dimensional interpolation calculation in the x direction or the y direction, the pixel value of the interpolation pixel P may be calculated by two-dimensional interpolation calculation. Furthermore, the pixel value of the interpolation pixel P may be calculated using not only the bicubic method but also a linear interpolation method, a nearest neighbor method, a bilinear method, or the like.

  In the second and third embodiments, the positive / negative relationship between the primary differences d1, d2, d3 and the secondary differences d4, d5 of four pixels adjacent in series is a peak, a valley, and others. In the case where it is determined that there is no edge between the two adjacent pixels G2 and G3, and the pixel value of the interpolation pixel P is calculated by the second interpolation calculation. The pixel value of the interpolated pixel P may be calculated by performing different interpolation calculations depending on whether or not the other is determined.

1 is a schematic block diagram showing the configuration of an image enlargement / reduction apparatus to which an edge detection apparatus according to a first embodiment of the present invention is applied. The figure which shows the pixel arrangement | sequence of the image represented by image data The figure which shows the example of difference filter Illustration for explaining the bicubic method The figure for demonstrating calculation of the pixel value of the interpolation pixel about the part determined to be an edge The flowchart which shows the process performed in 1st Embodiment. Schematic block diagram showing the configuration of an image enlargement / reduction apparatus to which an edge detection apparatus according to a second embodiment of the present invention is applied. The figure for demonstrating the filtering process performed in the filtering part in 2nd Embodiment. Table showing the relationship between the positive and negative of primary differences d1, d2, d3 and secondary differences d4, d5 and the profile shapes of four pixels adjacent in series (part 1) Table showing the relationship between the positive and negative of primary differences d1, d2, d3 and secondary differences d4, d5 and the profile shapes of four pixels adjacent in series (part 2) Table showing the relationship between the positive and negative of primary differences d1, d2, d3 and secondary differences d4, d5 and the profile shapes of four pixels adjacent in series (part 3) The flowchart which shows the process performed in 2nd Embodiment. Schematic block diagram showing the configuration of an image enlargement / reduction apparatus to which an edge detection apparatus according to a third embodiment of the present invention is applied. The figure which shows the example of the profile shape determined as an edge, although the difference of the pixel value of two adjacent pixels is very slight The flowchart which shows the process performed in 3rd Embodiment The schematic block diagram which shows the structure of the profile determination apparatus by the 4th Embodiment of this invention. The flowchart which shows the process performed in 4th Embodiment The schematic block diagram which shows the structure of the profile determination apparatus by the 5th Embodiment of this invention. The flowchart which shows the process performed in 5th Embodiment

Explanation of symbols

1,11,21,31,41 Input unit 2,12,22A, 22B, 32,42A, 42B Filtering unit 3,13,23,33,43 Judgment unit 4,14,24 Interpolation operation unit 5,15,25 , 35, 45 Control unit

Claims (9)

3 for each of the pixel values of the three pixel pairs by filtering each of the three pixel pairs including two adjacent pixels included in the four pixels adjacent in series on the image with a differential filter. Two primary differences d1, d2, and d3 are obtained, and two secondary differences d4 and d5 are obtained by performing filtering using the difference filter on two adjacent primary difference pairs in the three primary differences, respectively. Filtering means;
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-) , It is determined that an edge exists between the two central pixels of the four pixels adjacent in series, and there is no edge in other cases. An edge detection apparatus comprising: a detection means for determining 3 for each of the pixel values of the three pixel pairs by filtering each of the three pixel pairs including two adjacent pixels included in the four pixels adjacent in series on the image with a differential filter. Two primary differences d1, d2, and d3 are obtained, and two secondary differences d4 and d5 are obtained by performing filtering using the difference filter on two adjacent primary difference pairs in the three primary differences, respectively. First filtering means;
Second filtering means for obtaining a difference d0 of pixel values of the two central pixels by performing filtering processing by the differential filter on the central two pixels of the four pixels adjacent in series;
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-), And when the absolute value of the difference d0 between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value , between the two central pixels. edge detection device edge is determined that there exists, characterized by comprising a detecting means for determining that there is no edge otherwise to. In the pixels on the image, each of the pixel values of the three pixel pairs is obtained by performing filtering processing using a differential filter on three pixel pairs including two adjacent pixels included in four pixels adjacent in series. The three primary differences d1, d2, and d3 are obtained, and the filtering process by the difference filter is performed on each of the two adjacent primary difference pairs in the three primary differences to obtain two secondary differences d4 and d4. first filtering means for obtaining d5 ;
Second filtering means for obtaining a difference d0 between pixel values of the two central pixels by performing filtering processing using a differential filter on the central two pixels of the four pixels adjacent in series;
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-) And the four pixels adjacent in series when the absolute value of the difference d0 between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value. determines the profile shape of the pixel values in the vicinity of that edge, the profile judging device which is characterized in that a determining profile determination means that the shape other than the edge otherwise. 3 for each of the pixel values of the three pixel pairs by filtering each of the three pixel pairs including two adjacent pixels included in the four pixels adjacent in series on the image with a differential filter. Two primary differences d1, d2, and d3 are obtained, and two secondary differences d4 and d5 are obtained by performing filtering using the difference filter on two adjacent primary difference pairs in the three primary differences, respectively. ,
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-) , It is determined that an edge exists between the two central pixels of the four pixels adjacent in series, and there is no edge in other cases. An edge detection method, characterized in that 3 for each of the pixel values of the three pixel pairs by filtering each of the three pixel pairs including two adjacent pixels included in the four pixels adjacent in series on the image with a differential filter. Two primary differences d1, d2, and d3 are obtained, and two secondary differences d4 and d5 are obtained by performing filtering using the difference filter on two adjacent primary difference pairs in the three primary differences, respectively. ,
A filtering process using the difference filter is performed on the center two pixels of the four pixels adjacent in series to obtain a difference d0 between pixel values of the center two pixels,
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- , -, -, -, - it becomes either), when the absolute value of the difference d0 of the pixel values of two pixels of the center is equal to or greater than a predetermined threshold value, between two pixels of the central An edge detection method characterized in that it is determined that an edge is present, and in other cases it is determined that no edge exists . In the pixels on the image, each of the pixel values of the three pixel pairs is obtained by performing filtering processing using a differential filter on three pixel pairs including two adjacent pixels included in four pixels adjacent in series. The three primary differences d1, d2, and d3 are obtained, and the filtering process by the difference filter is performed on each of the two adjacent primary difference pairs in the three primary differences to obtain two secondary differences d4 and d4. d5
A filtering process using a difference filter is performed on the center two pixels of the four pixels adjacent in series to obtain a difference d0 between pixel values of the center two pixels,
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-) And the four pixels adjacent in series when the absolute value of the difference d0 between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value. A profile determination method characterized by determining that the profile shape of a neighboring pixel value is an edge, and otherwise determining that the profile shape is other than an edge . 3 for each of the pixel values of the three pixel pairs by filtering each of the three pixel pairs including two adjacent pixels included in the four pixels adjacent in series on the image with a differential filter. Two primary differences d1, d2, and d3 are obtained, and two secondary differences d4 and d5 are obtained by performing filtering using the difference filter on two adjacent primary difference pairs in the three primary differences, respectively. Procedure and
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-) , It is determined that an edge exists between the two central pixels of the four pixels adjacent in series, and there is no edge in other cases. A program for causing a computer to execute an edge detection method characterized in that 3 for each of the pixel values of the three pixel pairs by filtering each of the three pixel pairs including two adjacent pixels included in the four pixels adjacent in series on the image with a differential filter. Two primary differences d1, d2, and d3 are obtained, and two secondary differences d4 and d5 are obtained by performing filtering using the difference filter on two adjacent primary difference pairs in the three primary differences, respectively. Procedure and
A procedure of obtaining a difference d0 between pixel values of the two central pixels by performing filtering processing by the difference filter on the central two pixels of the four pixels adjacent in series;
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-), And when the absolute value of the difference d0 between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value , between the two central pixels. program for the edge is determined that there exists, to execute the edge detection method characterized by having a step of determining an edge does not exist in the computer otherwise to. In the pixels on the image, each of the pixel values of the three pixel pairs is obtained by performing filtering processing using a differential filter on three pixel pairs including two adjacent pixels included in four pixels adjacent in series. The three primary differences d1, d2, and d3 are obtained, and the filtering process by the difference filter is performed on each of the two adjacent primary difference pairs in the three primary differences to obtain two secondary differences d4 and d4. a procedure for obtaining d5 ;
A procedure of obtaining a difference d0 between pixel values of the two central pixels by performing filtering processing using a difference filter on the two central pixels of the four pixels adjacent in series;
The positive / negative relationship between the three primary differences d1, d2, d3 and the two secondary differences d4, d5 is (d1, d2, d3, d4, d5) = (+, +, +, +, −), (-,-,-,-, +), (+, +, +, +, +), (+, +, +,-,-), (-,-,-, +, +), (- ,-,-,-,-) And the four pixels adjacent in series when the absolute value of the difference d0 between the pixel values of the two central pixels is equal to or greater than a predetermined threshold value. A program for causing a computer to execute a profile determination method, comprising: determining a profile shape of a neighboring pixel value as an edge, and determining a shape other than an edge in other cases .

Images