- OpenCV - GUI
- OpenCV - Writing an Image
- OpenCV - Reading Images
- OpenCV - Storing Images
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Types of Images
Image Conversion
Drawing Functions
- OpenCV - Adding Text
- OpenCV - Drawing Arrowed Lines
- OpenCV - Drawing Convex Polylines
- OpenCV - Drawing Polylines
- OpenCV - Drawing an Ellipse
- OpenCV - Drawing a Rectangle
- OpenCV - Drawing a Line
- OpenCV - Drawing a Circle
Blur
Filtering
- OpenCV - Image Pyramids
- OpenCV - Morphological Operations
- OpenCV - Erosion
- OpenCV - Dilation
- OpenCV - Filter2D
- OpenCV - SQRBox Filter
- OpenCV - Box Filter
- OpenCV - Bilateral Filter
Thresholding
Sobel Derivatives
Transformation Operations
Camera and Face Detection
Geometric Transformations
Miscellaneous Chapters
OpenCV Useful Resources
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OpenCV - Sobel Operator
Using the sobel operation, you can detect the edges of an image in both horizontal and vertical directions. You can apply sobel operation on an image using the method sobel(). Following is the syntax of this method −
Sobel(src, dst, ddepth, dx, dy)
This method accepts the following parameters −
src − An object of the class Mat representing the source (input) image.
dst − An object of the class Mat representing the destination (output) image.
ddepth − An integer variable representing the depth of the image (-1)
dx − An integer variable representing the x-derivative. (0 or 1)
dy − An integer variable representing the y-derivative. (0 or 1)
Example
The following program demonstrates how to perform Sobel operation on a given image.
import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.imgcodecs.Imgcodecs; import org.opencv.imgproc.Imgproc; pubpc class SobelTest { pubpc static void main(String args[]) { // Loading the OpenCV core pbrary System.loadLibrary(Core.NATIVE_LIBRARY_NAME); // Reading the Image from the file and storing it in to a Matrix object String file ="E:/OpenCV/chap16/sobel_input.jpg"; Mat src = Imgcodecs.imread(file); // Creating an empty matrix to store the result Mat dst = new Mat(); // Applying sobel on the Image Imgproc.Sobel(src, dst, -1, 1, 1); // Writing the image Imgcodecs.imwrite("E:/OpenCV/chap16/sobel_output.jpg", dst); System.out.println("Image processed"); } }
Assume that following is the input image sobel_input.jpg specified in the above program.
![Window Input](/opencv/images/window_input.jpg)
Output
On executing the program, you will get the following output −
Image Processed
If you open the specified path, you can observe the output image as follows −
![Sobel Output](/opencv/images/sobel_output.jpg)
sobel Variants
On passing different values to the last to parameters (dx and dy) (among 0 and 1), you will get different outputs −
// Applying sobel on the Image Imgproc.Sobel(src, dst, -1, 1, 1);
The following table psts various values for the variables dx and dy of the method Sobel() and their respective outputs.
X-derivative | Y-derivative | Output |
---|---|---|
0 | 1 | ![]() |
1 | 0 | ![]() |
1 | 1 | ![]() |