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Hi,

hopefully my english is good enough for describing my problem. I am working only a short time on opencv. In a little project I tried to detect the number plates from cars. The detection works very well. Only the last function in my script throws an exception.

I tried to create a new mat from the picture and the rectangle but that throws the following exception: OpenCV Error: Assertion failed (0 <= roi.x && 0 <= roi.width && roi.x + roi.width <= m.cols && 0 <= roi.y && 0 <= roi.height && roi.y + roi.height <= m.rows) in cv::Mat::Mat, file ........\opencv\modules\core\src\matrix.cpp, line 323 Exception in thread "main" CvException [org.opencv.core.CvException: cv::Exception: ........\opencv\modules\core\src\matrix.cpp:323: error: (-215) 0 <= roi.x && 0 <= roi.width && roi.x + roi.width <= m.cols && 0 <= roi.y && 0 <= roi.height && roi.y + roi.height <= m.rows in function cv::Mat::Mat

But the detection works fine. the picture shows that the script creates rectangles around them.

Could somebody help me?

/*

* To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package demoOpenCV;

import java.util.ArrayList; import java.util.Iterator; import java.util.ListIterator; import org.opencv.core.Core; import org.opencv.core.CvType; import org.opencv.core.Mat; import org.opencv.core.MatOfPoint; import org.opencv.core.MatOfPoint2f; import org.opencv.core.Point; import org.opencv.core.Rect; import org.opencv.core.MatOfRect; import org.opencv.core.RotatedRect; import org.opencv.core.Scalar; import org.opencv.core.Size; import org.opencv.highgui.Highgui; import org.opencv.imgproc.Imgproc; import static org.opencv.imgproc.Imgproc.MORPH_RECT;

/**

• @author Manuel */ public class NumberPlate {

  public void run() { System.out.println("Kennzeichenerkennung is running...");

  Mat img = Highgui.imread("c:/tmp/plate2.jpg");
  Mat kopie = new Mat();
  img.copyTo(kopie);
  
  Mat img_grey = new Mat();
  
  Mat img_sobel = new Mat();
  
  Mat img_threshold = new Mat();
  
  Mat element = Imgproc.getStructuringElement(MORPH_RECT, new Size(17, 3));
  
  ArrayList<RotatedRect> rects = new ArrayList<RotatedRect>();
  ArrayList<MatOfPoint> contors = new ArrayList<MatOfPoint>();
  
  Mat schild;
  
  Imgproc.cvtColor(img, img_grey, Imgproc.COLOR_BGR2GRAY);
  
  Imgproc.blur(img_grey, img_grey, new Size(5, 5));
  
  Imgproc.Sobel(img_grey, img_sobel, CvType.CV_8U, 1, 0, 3, 1, 0);
  
  Imgproc.threshold(img_sobel, img_threshold, 0, 255,
          ((Imgproc.THRESH_OTSU) + (Imgproc.THRESH_BINARY)));
  
  Imgproc.morphologyEx(img_threshold, img_threshold, Imgproc.MORPH_CLOSE, element);
  
  Imgproc.findContours(img_threshold, contors, new Mat(), Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_NONE);
  
  ListIterator<MatOfPoint> it = contors.listIterator();
  while (it.hasNext()) {
      MatOfPoint2f mp2f = new MatOfPoint2f(it.next().toArray());
      RotatedRect mr = Imgproc.minAreaRect(mp2f);
      double area = Math.abs(Imgproc.contourArea(mp2f));
  
  double bbArea = mr.size.area();            
  double ratio = area / bbArea;            
  if ((ratio &lt; 0.45) || (bbArea &lt; 400)) {                
      it.remove();                
  } else {                
      rects.add(mr);                
  }
  
  
  }
  
  for (Iterator<RotatedRect> it1 = rects.iterator(); it1.hasNext();) {
      RotatedRect roRe = it1.next();
      Rect r = roRe.boundingRect();
  
  Core.rectangle(kopie, new Point((r.x), (r.y)),
          new Point((r.x + r.width), (r.y + r.height)),
          new Scalar(0, 0, 255));
  
  ***schild = kopie.submat(r);***
  Imgproc.blur ...