JP3065418B2 - Image processing apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method, and more particularly, to a method for supplying a digital image, performing a differential operation on the supplied digital image, calculating a differential image, and supplying the supplied image. The present invention relates to an image processing apparatus and a method for extracting an edge from a target included in an image. The present invention is applied to, for example, a robot that operates autonomously in a natural environment, a visual part of an autonomous vehicle, and the like. Here, the “edge” is a portion corresponding to a rapid change in density,
Edge extraction is used when performing feature extraction of an image, and is useful for understanding an object.

[0002]

2. Description of the Related Art Conventionally, there has been an image processing apparatus shown in FIG. As shown in the figure, the present apparatus includes an image supply unit 10 that supplies a digital image, an image differentiation processing unit 20 that performs a differential operation on the digital image supplied from the image supply unit 10 to calculate a differential image. And an edge extraction unit 114 that compares the absolute value of the pixel forming the differential image calculated by the differential processing unit 20 with a set threshold value and extracts an edge based on the comparison result. Things.

In an image processing apparatus according to a conventional example, an object may be present in both a sunny place and a shade in a natural image by using an edge in the image. In this case, the image supplied from the image supply unit 10 is differentiated by the differentiation processing unit 20, and the edge extraction unit 114 compares the absolute value of the value of the pixel with an appropriate threshold. The edge is extracted when the absolute value of the pixel is equal to or more than a certain appropriate threshold value.

[0004]

By the way, in the image processing apparatus according to the prior art, when the weather is fine in summer, the contrast between the sun and the shade is strong. For example, the illuminance is 100,000 lux (lx) in the sun and 4,000 lux in the shade, making it difficult to extract the edges of the sunlit object and the shaded object in the natural image in the same image plane. there were.

FIG. 13A shows, as an example, an original image of a road surface (when the density of a sunny road surface is higher than that of a shaded white line). Also, each density (almost equal to the illuminance) of the shaded road surface, the shaded white line, the sunlit road surface, and the sunlit white line is shown in FIG. From the original image shown in this example,
After extracting a differential image of the image, in order to extract an object in the sun, an edge is extracted from the differential image with an appropriate threshold value B. As shown in FIG. The absolute value of the differential value of the edge part of the object is the threshold B
Therefore, the edge cannot be extracted. Further, in order to extract an object in the shade, an edge is extracted from the differential image using an appropriate threshold value A.
As shown in FIG. 11D, an edge is detected on the entire surface in the sunshine area. This is because the reflection from the road surface and the white line in the sunshine area is caused by the instability of the density fluctuation in the minute part, as shown in FIG. It is because of that. Therefore, the conventional example has a problem that it is difficult to identify and extract an edge from an original image including both a shaded area and a sunlit area.

It is an object of the present invention to provide an image processing apparatus capable of extracting a high-quality edge from an image created under conditions including regions with different illuminances while eliminating the influence of different illuminances. The purpose is to be able to do.

[0007]

In order to solve the above technical problems, a first invention is, as shown in FIG. 1, provided with an image supply section 10 for supplying a digital image, and a differential section for supplying the supplied digital image. An image differential processing unit 20 that performs an operation to calculate a differential image, and extracts an edge from a target included in the supplied image. A specific illuminance area detection unit 30 that detects a specific illuminance area specified based on a comparison result between a value of a pixel forming a digital image including an existing object and a third threshold, a first threshold, and the differentiation processing A first threshold edge extraction unit 40 for extracting an edge based on a result of comparison with an absolute value of a pixel forming a differential image calculated by the unit 20; a second threshold different from the first threshold; Department The second threshold edge extraction unit 50 that extracts an edge based on the comparison result with the absolute value of the pixel forming the differential image calculated by 0 and the edge extracted by the first threshold edge extraction unit 40 are included. A specific illuminance region edge extraction unit 60 that extracts an edge portion within the specific illuminance region detected by the specific illuminance region detection unit 30 from the extracted image as an edge and does not extract an edge portion outside the region as an edge; Specific illuminance area edge extraction unit 6
It has an image synthesizing unit 70 for synthesizing the image including the edge extracted by 0 and the image including the edge extracted by the second threshold edge extracting unit 50.

On the other hand, the second invention, as shown in FIG.
A digital image is supplied (S1), and a differential operation is performed on the supplied digital image to calculate a differential image (S1).
2) In an image processing method for extracting an edge from an object included in a supplied image, a value of a pixel forming a digital image including an object present in both of at least two types of different illuminance regions and a value A specific illuminance area specified based on a comparison result with the three threshold values is detected (S3), and an edge is extracted based on a comparison result between the first threshold value and the calculated absolute value of the pixel forming the differential image. (S4),
Edge extraction is performed based on a comparison result between the second threshold value different from the first threshold value and the calculated absolute value of the pixel forming the differential image (S5), and based on the comparison result with the first threshold value. Only the edge portion within the specific illuminance area among the extracted edges is extracted as an edge (S6), and the image including the extracted edge based on the comparison result with the second threshold value and the specific illuminance area (S7).

[0009]

Next, the operation of the image processing apparatus according to the present invention will be described. In step S1, the image supply unit 10 supplies a digital image formed from pixels to each unit in the image processing apparatus. It is assumed that the digital image includes objects existing in both of at least two different illuminance regions. Here, the “target” refers to a portion of the image for which edge extraction is to be performed. In step S2, the image differentiating unit 20 performs a differentiating process on each pixel of the supplied image. For example,
If the value of the pixel at the position (x, y) (corresponding to the density value or the illuminance value) is f (x, y), the value f (x, y) of the pixel
F ′ (x, y) obtained by performing differential treatment in the vertical direction is, for example, f (x−1, y + 1) + f (x, y + 1) + f (x + 1, y + 1) ) -f (x-1, y-1)-
f (x, y-1) -f (x + 1, y-1). In step S3, the specific illuminance region detection unit 50 compares the set third threshold value with the supplied value of each pixel, and detects a specific illuminance region specified based on the comparison result. In the case described in claim 2, the value C is used as the third threshold value,
When the value of the supplied pixel is less than the value C, the detection is performed as a shade portion which is a specific illuminance region. In this case, the value C is set equal to an intermediate value between the two types of illuminance.

In step S4, the second threshold edge extracting unit 50
The second threshold value different from the first threshold value is compared with the value of the pixel forming the differential image calculated by the differential processing unit 20, and an edge is extracted based on the comparison result.
For example, in the case described in claim 2, the edge is extracted when it is smaller than the second threshold B (> first threshold A).

At the time of the operation in step S4, in step S5, the first threshold edge extracting unit 40 compares the first threshold with the value of the pixel forming the differential image, and based on the comparison result, determines the edge. Is extracted. For example, in the case described in claim 2, the value of a pixel forming a differential image calculated by the differential processing unit 20 is a value B that is a second threshold value.
An edge is extracted when it is smaller than. Step S6
Then, among the edges extracted by the first threshold edge extracting unit 40, only the edge portions in the region specified in step S3 are extracted by the specific illuminance region edge extracting unit 60. In step S7, the image including the edge extracted by the second threshold edge extracting unit 50 and the image including the edge extracted by the specific illuminance region edge extracting unit 60 by the image combining unit 70. Is performed. The reason for this configuration is that in regions having different illuminances, threshold values for extracting a target edge from a differential image are different from each other.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image processing apparatus according to an embodiment of the present invention will be described. FIG. 3 illustrates an example of a device configuration block diagram of the image processing apparatus according to the present embodiment. As shown in the figure, the image processing apparatus according to the present embodiment reads a program memory 52 in which various control programs are stored, an image processing target, and outputs digitized image data. An image reading unit 53, a recording unit 55 for recording and outputting image-processed data, an image memory 54 for storing read digital images, a display unit 56 for displaying processing results and the like, and performing operation instructions It has an operation panel 57 and a CPU 51 that performs various controls based on the program.

FIG. 4 is a functional block diagram of the image processing apparatus according to the first embodiment. As shown in the figure, in the present embodiment, an image supply unit 1 for supplying a digital image, and an image differentiation unit for performing a differential operation on the digital image supplied from the image supply unit 1 to calculate a differential image A shading part formed by the processing unit 2 and a pixel having a value less than a third threshold value C that forms a digital image including a target that is present in both two types of different illuminance areas, ie, a shade area and a sunshine area. (Particular illuminance area) detection of a shaded part 3
And a threshold A edge extraction for extracting an edge when an absolute value of a pixel forming a differential image calculated by the differential processing unit 2 is larger than a first threshold A smaller than a second threshold B A threshold B edge extracting unit 5 for extracting an edge when the absolute value of the pixel forming the differential image calculated by the differential processing unit 2 is larger than the value B which is the second threshold A shade portion edge extractor 6 that extracts an edge portion within a shade portion, which is a specific illuminance region, from the edges extracted by the threshold A edge extractor 4 and does not extract an edge portion within a sunlit portion; An image combining unit 7 for combining an image including the edge extracted by the specific illuminance region edge extracting unit 6 and an image including the edge extracted by the threshold B edge extracting unit 5. is there

Here, the image supply section 1 corresponds to the image reading section 53, and the image differentiation processing section 2, the shade portion detection section 3, the threshold A edge extraction section 4, the threshold B edge extraction section 5,
The shade portion edge extraction unit 6 and the image synthesis unit 7
PU 51, program memory 52, and image memory 5
This is equivalent to 4. In this example, FIG.
A description will be given of a case where, for an image related to a road surface on which a white line in the sun and shade shown in FIG. In this case, the illuminance of the shaded white line is smaller than the illuminance of the sunny road surface, and the thresholds A, B and C are set as shown in FIG. That is, the threshold value A is a value necessary for extracting the edge of the white line in the shade portion, and needs to be set to a value equal to or less than the difference between the illuminance (density) of the shade white line and the illuminance of the shade road surface. The threshold value B is a value necessary for extracting the edge of the white line in the sunlit part, and is set to a value that is equal to or less than the difference between the illuminance of the sunlit white line and the illuminance of the sunlit road surface, and is larger than the threshold value B. Need to be The threshold value C is a value necessary for separating the sunlit portion from the shaded portion, and is set to a value between the illuminance of the shaded white line and the illuminance of the sunlit road surface. Note that, as shown in FIG. 13B, in the sunlit part, unlike the shaded part, the spatial variation of the illuminance is severe due to the reflection. FIG. 6 illustrates an example in which image processing is performed by the image processing apparatus according to the first embodiment under such a premise.

The shade portion detector 3 performs binarization based on the threshold value C shown in FIG.
The shaded part and the sunlit part are separated, and an area smaller than the threshold value C is detected as a shaded part as shown in FIG. On the other hand, the threshold A edge extraction unit 4 extracts an edge by comparing the absolute value of the pixel value subjected to the differentiation processing by the differentiation processing unit 2 with the threshold A. For the extracted edges, the shade portion edge extraction unit 6 extracts an edge portion in the shade portion detected by the shade portion detection unit 3 as an edge, and does not extract an edge portion in a sunshine portion as an edge. The result is as shown in FIG. Further, when the threshold B edge extracting unit 5 synthesizes the differential image with the image including the edge shown in FIG. 6C extracted by the threshold B from the differential image by the image synthesizing unit 7, FIG. The composite image shown in f) is obtained.

Next, a second embodiment will be described.
In this example, as shown in FIG. 5, unlike the first embodiment, the pixel shrinking / expanding unit 13 that shrinks or expands the pixels forming the shaded portion detected by the shaded portion detection unit 3 according to an instruction is provided. It is provided. That is, the shade portion detection unit 3 detects all portions below the threshold value C as shade portions and obtains the shade portion of FIG. 6A, but unlike the first embodiment, the present embodiment differs from the first embodiment. , The pixel contraction / expansion unit 13
To shrink the detected shade area by 2-3 pixels,
The edge of the boundary between the shade and the sun is deleted as shown in FIG. When an edge is extracted with a threshold value A by the shaded portion edge extracting unit 6 from the shaded portion deleted by a few pixels in this manner, the result is as shown in FIG. ), It is possible to obtain a synthesized image having no edge at the boundary between the shaded portion and the sunlit portion.

FIG. 7 shows a second example of the second embodiment. In the present example, the pixel contraction / expansion unit 13 is provided as in the first example of the second embodiment, and the pixel is formed from pixels having a value less than the value C shown in FIG. Instead of the shade portion detection unit 3 that detects a particular illuminance region as a shade portion, a particular illuminance region formed from pixels having a value less than the value D as a third threshold is detected as a shade portion as shown in FIG. 7B. A shading part detecting unit 30 is provided. That is, in the present embodiment, as shown in FIG. 7B, unlike the first embodiment, on the assumption that the illuminance of the shaded white line is larger than the illuminance of the sunny road surface, the third threshold value D Is set to be larger than the illuminance on a shaded road surface and smaller than the illuminance on a sunny road surface. By using the shade part detection unit 30, a shade part is detected as shown in FIG. 7C, and a shade white line part is not extracted as shade. Therefore, even if the shaded portion edge extraction unit 6 performs the edge extraction with the threshold value A in the shaded portion, there is a high possibility that the edge is cut finely. Therefore, as shown in FIG.
When the extracted shade portion is expanded by 2 to 3 pixels by the pixel contraction / expansion unit 13 and the edge is extracted with the threshold value A for the portion, the result is as shown in FIG. The part will be completely covered. By synthesizing the image and the image extracted with the threshold B by the image synthesizing unit 7, a high-quality edge synthesized image can be obtained.

FIG. 8 shows a third example according to the second embodiment. In this example, as shown in FIG. 8A, an edge is extracted when a white line is partially shaded. As in the second example of the second embodiment shown in FIG. 7,
FIG. 8 (d) shows a shaded portion by the pixel contraction / expansion unit 13.
Is expanded as shown in FIG.
Then, an edge in the shaded area is extracted as shown in FIG. 9E, and the extracted edge and the edge extracted by the threshold B edge extraction unit 5 are synthesized by the image synthesis unit 7, A composite image shown in FIG.

Next, a third embodiment will be described.
As shown in FIG. 9, in this example, in order to supply an image, a TV camera 21a, an A / D converter 21b that digitizes analog data read from the camera 21a, and an interlaced image ( The image supply unit 21 includes a non-interlace conversion unit 21c that converts an image on which the interlaced scanning process has been performed) into a non-interlace image. Further, a binarizing unit 23 corresponding to the shade part detecting unit 3 for binarizing the supplied image, and a pixel shrinking / expanding unit 13
The first maximum value filter unit 33a, the second maximum value filter unit 33b, and the third maximum value filter unit 33c corresponding to
And Further, a first spatial filter unit 22a corresponding to the image differentiation processing unit 2 of the first embodiment and the second embodiment,
And a second spatial filter unit 22b, a first inter-pixel operation unit 24 corresponding to the threshold A edge unit 4 and the threshold B edge unit 5 of the first and second embodiments, and the shaded part edge extraction unit 6 and a second inter-pixel calculation unit 26 corresponding to the second pixel calculation unit 26. Here, the spatial filters I and II used in the first spatial filter unit 22a and the second spatial filter unit 22b are respectively shown in FIG.
Filtering is performed with the coefficient shown in FIG.
As an output of the spatial filter I, a differential value in the horizontal direction of the image is output, and as an output of the spatial filter II, a differential value in the vertical direction of the image is output. Further, the binarization unit 23 separates a shaded portion “0” and a sunlit portion “1” by a certain threshold value C. The first inter-pixel calculation unit 24 extracts positive / negative edges in the horizontal / vertical directions based on the thresholds A and B.

That is, when the output of the spatial filter I of the first spatial filter section 22a is B or more, the positive edge is increased in the vertical direction and the least significant bit is turned on "1". The positive edge is small, the second bit is in the ON state "1", the vertical direction negative edge is large when the output is -B or less, and the third bit is in the ON state "1" when the output is -A or less. When the negative edge is small, the fourth bit is turned on “1”, and the second spatial filter
When the output of the spatial filter II of b is greater than or equal to B, the positive edge in the horizontal direction is large, the fifth bit is in the on state "1", and when the output is greater than A, the positive edge in the horizontal direction is small, and the sixth bit is in the on state "1". When the output is -B or less, the negative edge in the horizontal direction is large, the seventh bit is turned on "1", and the output is -A
In the following cases, a signal in which the horizontal negative edge is small and the eighth bit is in the ON state “1” is output and sent to the second inter-pixel calculation unit 26.

The minimum value filter and the maximum value filter used in the pixel contraction / expansion unit 33 will be described. The minimum value filter performs a process of setting the middle pixel value to “0” if there is a pixel having a value of “0” within the window of 3 × 3 pixels. The sunlit part of the output of the binarization is contracted by three pixels (conversely, the shaded part is dilated). On the other hand, the maximum value filter sets the middle pixel value to “1” when the value “1” exists in the window. Is expanded by three pixels (conversely, the shaded part is contracted).

When the binarized output is "1", the second inter-pixel operation section 26 outputs the second and second outputs of the first inter-pixel operation section 24.
Bits 4, 6, and 8 are turned off, and the first, third, fifth, and seventh bits of the output of the first inter-pixel arithmetic unit 24 are set to "0" when the binarized output is "0". And The resulting output is the positive vertical edge of the sun when the least significant bit is on, the vertical positive edge of the shade when the second bit is on, and the vertical vertical edge when the third bit is on. A negative edge, a negative vertical edge in the shade when the fourth bit is on, a positive horizontal edge in the sun when the fifth bit is on, and a positive horizontal edge in the shade when the sixth bit is on. When the seventh bit is on, it represents a negative horizontal edge in the sun, and when the eighth bit is on, it represents a negative horizontal edge in the shade. Therefore,
Depending on whether the output value of the binarization unit 23 is "1" or "0", an edge in a sunlit part and an edge in a shaded part are obtained, respectively. By combining the edges thus obtained, it is possible to obtain an edge from which the influence of different illuminance is eliminated. Based on the output result of the second inter-pixel operation unit 26, it is possible to extract an edge of a sunlit portion or a shaded portion for each pixel.
As described above, in the present embodiment, by providing the pixel contraction / expansion portion, the edge generated from the boundary between the shade and the sunlit portion can be easily removed.
High quality edges can be obtained. As described above, in the second embodiment and the third embodiment, by providing the pixel contraction / expansion units 13 and 23,
Edges other than the object whose edge is to be obtained can be removed. Therefore, it is possible to obtain a high-quality edge in which noise based on the influence of the difference in illuminance is not reflected in the image.

FIG. 11 shows a fourth embodiment. In this example, image processing for edge extraction is performed in response to the case where there are three types of portions having different illuminances. That is, when the three types of regions having different illuminances are a normal region, a first region, and a second region, as shown in FIG.
Instead of the first area detection unit 43a that detects the first area specified based on the comparison result between the supplied pixel value forming the digital image and the threshold value E, based on the comparison result with the threshold value F A second area detection unit 43b for detecting the specified second area. Further, the threshold A
Instead of the edge extracting unit 4, a threshold G different from the threshold B
A threshold G edge extraction unit 34a for extracting an edge based on a comparison result between the absolute value of the pixel forming the differential image calculated by the differential processing unit 2 and a threshold H different from the threshold G and the threshold B A threshold H edge extraction unit 34b for extracting an edge based on a result of comparison with the absolute value of a pixel forming a differential image. Further, instead of the shaded part edge extraction unit 6, the threshold G edge extraction unit 34
a of the first region detection unit 4
3a, a first area edge extraction unit 36a that extracts only edges within the first area detected by the first area 3a, and an edge extracted by the second area detection unit 43b among the edges extracted by the threshold H edge extraction unit 34b. And a second area edge extraction unit 36b for extracting only the edges within the second area. In this example, it is possible to extract the target edge of an image including three or more types of regions having different illuminances while eliminating the influence of the different illuminances. In addition, the first, second,
In the third and fourth embodiments, edges in both the shaded portion and the sunlit portion are extracted. However, edges in only the shaded portion or only the sunlit portion may be extracted. .

[0024]

As described above, according to the present invention, the specific illuminance area detecting section, the first threshold edge extracting section,
The second threshold edge extracting unit and the specific illuminance region edge extracting unit extract edges with different threshold values in the specific illuminance region and other regions, and synthesize an image including these edges by the image synthesizing unit. Like that. Therefore, even when an object whose edge is to be obtained exists in at least two types of different illuminance regions, a high-quality edge can be extracted by eliminating the influence of the different illuminance.

[Brief description of the drawings]

FIG. 1 is a block diagram of the principle of the first invention.

FIG. 2 is a flowchart of the principle of the second invention.

FIG. 3 is a block diagram of a device configuration according to the embodiment.

FIG. 4 is a block diagram according to a first embodiment;

FIG. 5 is a block diagram according to a second embodiment;

FIG. 6 is a diagram showing image processing according to a first example of the first embodiment and the second embodiment.

FIG. 7 is a diagram illustrating a second example of image processing according to the second embodiment;

FIG. 8 is a diagram illustrating a third example of image processing according to the second embodiment;

FIG. 9 is a block diagram according to a third embodiment.

FIG. 10 is a diagram illustrating an example of a spatial filter according to a third embodiment.

FIG. 11 is a block diagram according to a fourth embodiment.

FIG. 12 is a block diagram according to a conventional example.

FIG. 13 is a diagram showing image processing according to a conventional example.

[Explanation of symbols]

10, 1 image supply unit 20, 2 image differentiation processing unit 30 (3) specific illuminance area detection unit (shade part detection unit) 40 (4) first threshold edge extraction unit (threshold A edge extraction unit) 50 (5) Two-threshold edge extraction unit (threshold B edge extraction unit) 60 (6) Specific illuminance area edge extraction unit (shade portion edge extraction unit) 70,7 Image synthesis unit

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Claims (4)

(57) [Claims] An image supply unit (1) for supplying a digital image.
0) and an image differential processing unit (20) for performing a differential operation on the supplied digital image to calculate a differential image, and extracting an edge from a target included in the supplied image. In the apparatus, a specific illuminance area specified based on a comparison result between a value of a pixel forming a digital image including a target present in at least two different illuminance areas and a third threshold value is detected. Edge extraction is performed based on a comparison result of the specific illuminance area detection unit (30), the first threshold value, and the absolute value of the pixel forming the differential image calculated by the differentiation processing unit (20). First threshold edge extraction unit (4
0), a second threshold different from the first threshold, and the differential processing unit (2
A second threshold edge extracting unit (50) for extracting an edge based on a comparison result between the absolute value of the pixel forming the differential image calculated in step (0) and the first threshold edge extracting unit (40) An edge portion within the specific illuminance region detected by the specific illuminance region detection unit (30) is extracted as an edge from the image including the extracted edge, and an edge portion outside the region is not extracted as an edge. An illuminance area edge extraction unit (60), an image including an edge extracted by the specific illuminance area edge extraction unit (60), and a second threshold edge extraction unit (50)
An image synthesizing unit (70) for synthesizing an image including an edge extracted by the image synthesis method. 2. The specific illuminance area detection section (30) detects a specific illuminance area formed from pixels whose digital image forming pixels are smaller than a value C which is a third threshold value as a shade portion. The value A that is the first threshold is set to be smaller than the value B that is the second threshold, and the first threshold edge extraction unit (40) performs the differentiation calculated by the differentiation processing unit (20). The edge extraction is performed when the absolute value of the value of the pixel forming the image is larger than the value A which is the first threshold, and the second threshold edge extraction unit (50) is the differential processing unit (20). 2. The image processing apparatus according to claim 1, wherein the edge is extracted when the absolute value of the value of the pixel forming the differential image calculated by the above is larger than the value B which is the second threshold value. 3. A pixel reduction / expansion unit for reducing or expanding the specific illuminance area detected by the specific illuminance area detection unit (30) in a vertical or horizontal direction by a predetermined number of pixels according to an instruction. The image processing apparatus according to claim 1, wherein: 4. A digital image is supplied (S1), a differential operation is performed on the supplied digital image to calculate a differential image (S2), and an edge is extracted from an object included in the supplied image. In the image processing method, detection of a specific illuminance area specified based on a comparison result of a pixel value forming a digital image including a target present in at least two types of different illuminances and a third threshold value is performed. Performing (S3), extracting an edge based on a comparison result of the first threshold value and the absolute value of the pixel value forming the calculated differential image (S4), and extracting a second threshold value different from the first threshold value An edge is extracted based on a comparison result between the calculated absolute value of the pixel forming the differential image and the calculated absolute value of the pixel (S5). Within the specific illuminance area Only the edge portion is extracted as an edge (S6), and an image including the edge extracted based on the comparison result with the second threshold and an image including the edge portion in the specific illuminance region are combined. (S7).