OpenCV - Scharr Operator


Scharr is also used to detect the second derivatives of an image in horizontal and vertical directions. You can perform scharr operation on an image using the method scharr(). Following is the syntax of this method −

Scharr(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)


The following program demonstrates how to apply scharr to a given image.

import org.opencv.core.Core;
import org.opencv.core.Mat;

import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;

public class ScharrTest {

   public static void main( String[] args ) {

      // Loading the OpenCV core library
      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 Box Filter effect on the Image
      Imgproc.Scharr(src, dst, Imgproc.CV_SCHARR, 0, 1);

      // Writing the image
      Imgcodecs.imwrite("E:/OpenCV/chap16/scharr_output.jpg", dst);

      System.out.println("Image processed");

Assume that following is the input image scharr_input.jpg specified in the above program.

Window Input


On executing it, you will get the following output −

Image Processed

If you open the specified path you can observe the output image as follows −

Scharr Output

More scharr Derivatives

On passing different values to the last to parameters (dx and dy) (among 0 and 1) you will get different outputs −

// Applying scharr on the Image
Imgproc.Scharr(src, dst, -1, 1, 1);

Following is a table listing various values for the variables dx and dy of the method scharr() and their respective outputs.

X-derivative Y-derivative Output
0 1 Scharr 01
1 0 Scharr 10