Question

I’m running OpenCV 2.4.2, on Visual Studio 2012. I want to use MSER to detect text in images. I started off with the sample MSER sample program provided in the OpenCV directory,

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
#include <stdio.h>

using namespace cv;
using namespace std;

static const Vec3b bcolors[] =
{
    Vec3b(0,0,255),
    Vec3b(0,128,255),
    Vec3b(0,255,255),
    Vec3b(0,255,0),
    Vec3b(255,128,0),
    Vec3b(255,255,0),
    Vec3b(255,0,0),
    Vec3b(255,0,255),
    Vec3b(255,255,255)
};

int main( int argc, char** argv )
{
    string path;
    Mat img0, img, yuv, gray, ellipses;

    img0 = imread( argc != 2 ? "puzzle.png" : argv[1], 1 );
    if( img0.empty() )
    {
        if( argc != 2 )
            cout << "\nUsage: mser_sample <path_to_image>\n";
        else
            cout << "Unable to load image " << argv[1] << endl;
        return 0;
    }

    cvtColor(img0, yuv, COLOR_BGR2YCrCb);
    cvtColor(img0, gray, COLOR_BGR2GRAY);
    cvtColor(gray, img, COLOR_GRAY2BGR);
    img.copyTo(ellipses);

    vector<vector<Point> > contours;
    double t = (double)getTickCount();
    MSER()(yuv, contours);
    t = (double)getTickCount() - t;
    printf( "MSER extracted %d contours in %g ms.\n", (int)contours.size(),
           t*1000./getTickFrequency() );

    // draw mser's with different colors
    for( int i = (int)contours.size()-1; i >= 0; i-- )
    {
        const vector<Point>& r = contours[i];
        for ( int j = 0; j < (int)r.size(); j++ )
        {
            Point pt = r[j];
            img.at<Vec3b>(pt) = bcolors[i%9];
        }

        // find ellipse (it seems cvfitellipse2 have error or sth?)
        RotatedRect box = fitEllipse( r );

        box.angle=(float)CV_PI/2-box.angle;
        ellipse( ellipses, box, Scalar(196,255,255), 2 );
    }

    imshow( "original", img0 );
    imshow( "response", img );
    imshow( "ellipses", ellipses );

    waitKey(0);
}

When I build and run this code, I get the following output after which the application stops responding:

 MSER extracted 1584 contours in 1748.41 ms.
 OpenCV Error: Assertion failed (points.checkVector(2) >= 0 && (points.depth() == 
 CV_32F || points.depth() == CV_32S)) in unknown function, file 
 ..\..\..\src\opencv\modules\imgproc\src\contours.cpp, line 2019

Any idea what exactly the problem is? I am totally lost!

I’ve tried commenting out everything inside the outer for loop, and it seems that the problem lies with the RotatedRect and fitEllipse portions. I’m not completely sure though.Any help would be much appreciated!

Answer 1

You may double check the data type of your variables. From the error message, some function can only take Mat variable with either CV_32F or CV_32S.