OpenCV - Rotation


You can perform rotation operation on an image using the warpAffine() method of the imgproc class. Following is the syntax of this method −

Imgproc.warpAffine(src, dst, rotationMatrix, size);

This method accepts the following parameters −

  • src − A Mat object representing the source (input image) for this operation.

  • dst − A Mat object representing the destination (output image) for this operation.

  • rotationMatrix − A Mat object representing the rotation matrix.

  • size − A variable of the type integer representing the size of the output image.


The following program demonstrates how to rotate an image.

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

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

public class Rotation {
   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/chap24/transform_input.jpg";
      Mat src = Imgcodecs.imread(file);

      // Creating an empty matrix to store the result
      Mat dst = new Mat();

      // Creating a Point object
      Point point = new Point(300, 200)

      // Creating the transformation matrix M
      Mat rotationMatrix = Imgproc.getRotationMatrix2D(point, 30, 1);

      // Creating the object of the class Size
      Size size = new Size(src.cols(), src.cols());

      // Rotating the given image
      Imgproc.warpAffine(src, dst, rotationMatrix, size);

      // Writing the image
      Imgcodecs.imwrite("E:/OpenCV/chap24/rotate_output.jpg", dst);

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

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

Transform Input


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 −

Rotate Output