Java DIP Sobel Operator - Digital image processing

What is Sobel Operator?

Sobel operator is equal to Prewitt operator. It is also used for edge detection. Sobel operator is mainly applied to find out two kinds of edges in an image: Vertical direction edges and Horizontal direction edges.

Here we use OpenCV function filter2D to apply Sobel operator to images. uYou can find these functions nder Imgproc package. Its syntax is given below:

The function arguments are described below:

Sr.No. Argument
1

src

It is source image.

2

dst

It is destination image.

3

ddepth

It is the depth of dst. A negative value (such as -1) indicates that the depth is the same as the source.

4

kernel

It is the kernel to be scanned through the image.

5

anchor

It is the position of the anchor relative to its kernel. The location Point (-1, -1) indicates the center by default.

6

delta

It is a value to be added to each pixel during the convolution. By default it is 0.

7

BORDER_DEFAULT

We let this value by default.

Other than the filter2D method, the other methods used by the Imgproc class are described briefly:

Sr.No. Methods
1

cvtColor(Mat src, Mat dst, int code, int dstCn)

It converts an image from one color space to another.

2

dilate(Mat src, Mat dst, Mat kernel)

It dilates an image by using a specific structuring element.

3

equalizeHist(Mat src, Mat dst)

It equalizes the histogram of a grayscale image.

4

filter2D(Mat src, Mat dst, int ddepth, Mat kernel, Point anchor, double delta)

It convolves an image with the kernel.

5

GaussianBlur(Mat src, Mat dst, Size ksize, double sigmaX)

It blurs an image using a Gaussian filter.

6

integral(Mat src, Mat sum)

It calculates the integral of an image.

Example

Below mentioned example describes the use of Imgproc class to perform Sobel operator to an image of Grayscale.

Output

After executing the above code, the following output is seen:

Original Image

originalimage

This original image is convolved with the Sobel operator of vertical edges, which is given below:

Vertical Direction

-

-1 0 1
-2 0 2
-1 0 1

Convolved Image(Vertical Direction)

Convolved Image(Vertical Direction)

This original is convolved with the Sobel operator of horizontal edges, which is given below:

Horizontal Direction

1 -2 -1
0 0 0
1 2 1

Convolved Image(Horizontal Direction)

Convolved Image(Horizontal Direction)

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Digital image processing Topics