How to match keypoints of two images using OpenCV Java library?

org.opencv.features2d.Feature2D (Abstract) class’s detect() method detects key points of a given image. For this method, you need to pass a Mat object representing the source image and an empty MatOfKeyPoint object to hold the read keypoints.

org.opencv.features2d.Feature2D The strong>drawMatches() method of class finds matches between key points of two given images and draws them. This method accepts the following parameters -

• src1 - an object source image representing the first Mat class.

• keypoints1 - Object of class MatOfKeyPoint, representing the key point of the first source image.

• src2 - An object of class Mat representing the second source image.

• keypoints2 - Object of class MatOfKeyPoint, representing the key points of the second source image.

• matches1to2 strong> - a match from the first image to the second image, meaning keypoints1[i] is in keypoints2[matches[i] ] There are corresponding points in .

• dst - An object of Mat class representing the target image.

So, matching the key points of two images -

• Read the two sources using the imread() method image.

• Get the key points of the image and use the detect() method to draw two images.

• Use the drawMatches() method to find and draw matches.

Example

import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfDMatch;
import org.opencv.core.MatOfKeyPoint;
import org.opencv.features2d.FastFeatureDetector;
import org.opencv.features2d.Features2d;
import org.opencv.highgui.HighGui;
import org.opencv.imgcodecs.Imgcodecs;
public class MatchingKeypoints {
   public static void main(String args[]) throws Exception {
      //Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
      //Reading the source images
      String file1 ="D:\Images\feature1.jpg";
      Mat src1 = Imgcodecs.imread(file1);
      String file2 ="D:\Images\feature2.jpg";
      Mat src2 = Imgcodecs.imread(file2);
      //Creating an empty matrix to store the destination image
      Mat dst = new Mat();
      FastFeatureDetector detector = FastFeatureDetector.create();
      //Detecting the key points in both images
      MatOfKeyPoint keyPoints1 = new MatOfKeyPoint();
      detector.detect(src1, keyPoints1);
      MatOfKeyPoint keyPoints2 = new MatOfKeyPoint();
      detector.detect(src2, keyPoints2);
      MatOfDMatch matof1to2 = new MatOfDMatch();
      Features2d.drawMatches(src1, keyPoints1, src2, keyPoints2, matof1to2, dst);
      HighGui.imshow("Feature Matching", dst);
      HighGui.waitKey();
   }
}

Input image

Image1 -

Image2 -

Output

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