TemplateMatching.java

package matching;
import org.bytedeco.javacv.*;
import org.bytedeco.javacpp.*;
import org.bytedeco.javacpp.indexer.FloatIndexer;

import static org.bytedeco.javacpp.opencv_core.*;
import static org.bytedeco.javacpp.opencv_imgproc.*;
import static org.bytedeco.javacpp.opencv_highgui.*;
import static org.bytedeco.javacpp.opencv_imgcodecs.*;
import static org.bytedeco.javacpp.opencv_calib3d.*;
import static org.bytedeco.javacpp.opencv_objdetect.*;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

/**
 * Example of template javacv (opencv) template matching using the last java build
 *
 * We need 2 default parameters like this (source image, image to find )
 * "C:\Users\Waldema\Desktop\bg.jpg" "C:\Users\Waldema\Desktop\imageToFind.jpg" 
 *
 * @author Waldemar Neto
 */
public class TemplateMatching {

    public static void main(String[] args) throws Exception {
        
        newStyle(args);
        //oldStyle(args);
   
    }
    

    
    public static void newStyle(String[] args){
        //read in image default colors
        Mat sourceColor = imread(args[0]);
        Mat sourceGrey = new Mat(sourceColor.size(), CV_8UC1);
       cvtColor(sourceColor, sourceGrey, COLOR_BGR2GRAY);
       //load in template in grey 
       Mat template = imread(args[1],CV_LOAD_IMAGE_GRAYSCALE);//int = 0
       //Size for the result image
       Size size = new Size(sourceGrey.cols()-template.cols()+1, sourceGrey.rows()-template.rows()+1);
       Mat result = new Mat(size, CV_32FC1);
       matchTemplate(sourceGrey, template, result, TM_CCORR_NORMED);
       
       DoublePointer minVal= new DoublePointer();
       DoublePointer maxVal= new DoublePointer();
       Point min = new Point();
       Point max = new Point();
       minMaxLoc(result, minVal, maxVal, min, max, null);
       rectangle(sourceColor,new Rect(max.x(),max.y(),template.cols(),template.rows()), randColor(), 2, 0, 0);
       
       imshow("Original marked", sourceColor);
       imshow("Ttemplate", template);
       imshow("Results matrix", result);
       waitKey(0);
       destroyAllWindows();
        
    }

    // some usefull things.
    public static Scalar randColor(){
       int b,g,r;
       b= ThreadLocalRandom.current().nextInt(0, 255 + 1);
       g= ThreadLocalRandom.current().nextInt(0, 255 + 1);
       r= ThreadLocalRandom.current().nextInt(0, 255 + 1);
       return new Scalar (b,g,r,0);
    }
    
    public static List<Point> getPointsFromMatAboveThreshold(Mat m, float t){
       List<Point> matches = new ArrayList<Point>();
       FloatIndexer indexer = m.createIndexer();
       for (int y = 0; y < m.rows(); y++) {
            for (int x = 0; x < m.cols(); x++) {
               if (indexer.get(y,x)>t) {
              System.out.println("(" + x + "," + y +") = "+ indexer.get(y,x));
              matches.add(new Point(x, y));
          }
         }
       }
       return matches;
    }
    
    public static void oldStyle(String[] args){
        //get color source image to draw red rect on later
        IplImage srcColor = cvLoadImage(args[0]);
        //create blank 1 channel image same size as the source 
        IplImage src = cvCreateImage(cvGetSize(srcColor), IPL_DEPTH_8U, 1);
        //convert source to grey and copy to src
        cvCvtColor(srcColor, src, CV_BGR2GRAY);
        //get the image to match loaded in greyscale. 
        IplImage tmp = cvLoadImage(args[1], 0);
        //this image will hold the strength of the match
        //as the template is translated across the image 
        IplImage result = cvCreateImage(
                        cvSize(src.width() - tmp.width() + 1,
                        src.height() - tmp.height() + 1), IPL_DEPTH_32F, src.nChannels());

        cvZero(result);

        // Match Template Function from OpenCV
        cvMatchTemplate(src, tmp, result, CV_TM_CCORR_NORMED);

        // double[] min_val = new double[2];
        // double[] max_val = new double[2];
        DoublePointer min_val = new DoublePointer();
        DoublePointer max_val = new DoublePointer();

        CvPoint minLoc = new CvPoint();
        CvPoint maxLoc = new CvPoint();

        cvMinMaxLoc(result, min_val, max_val, minLoc, maxLoc, null);

        // Get the Max or Min Correlation Value
        // System.out.println(Arrays.toString(min_val));
        // System.out.println(Arrays.toString(max_val));

        CvPoint point = new CvPoint();
        point.x(maxLoc.x() + tmp.width());
        point.y(maxLoc.y() + tmp.height());
        // cvMinMaxLoc(src, min_val, max_val,0,0,result);

        cvRectangle(srcColor, maxLoc, point, CvScalar.RED, 2, 8, 0); // Draw a
                                                                // Rectangle for
                                                                // Matched
                                                                // Region

        cvShowImage("Lena Image", srcColor);
        cvWaitKey(0);
        cvReleaseImage(srcColor);
        cvReleaseImage(src);
        cvReleaseImage(tmp);
        cvReleaseImage(result);
    }
}