'System.Runtime.InteropServices.SEHException' unhandled exception in OpenCV code

I'm now using VC++2008 and OpenCV2.1 on Windows 7. I'm trying out the facedetect.cpp example. When I run the program, it throws up a messagebox saying:

An unhandled exception of type 'System.Runtime.InteropServices.SEHException' occurred in Test Console 2.exe

Additional information: External component has thrown an exception.

Here's the entire code:

#include "stdafx.h"
#include "cv.h"
#include "highgui.h"
#include <iostream>
#include <cstdio>
using namespace std;
using namespace cv;

void detectAndDraw( Mat& img,
                   CascadeClassifier& cascade, CascadeClassifier& nestedCascade,
                   double scale);

String cascadeName =
"C:/OpenCV2.1/data/haarcascades/haarcascade_frontalface_alt.xml";
String nestedCascadeName =
"C:/OpenCV2.1/data/haarcascades/haarcascade_eye_tree_eyeglasses.xml";

int main( int argc, const char** argv )
{
    CvCapture* capture = 0;
    Mat frame, frameCopy, image;
    const String scaleOpt = "--scale=";
    size_t scaleOptLen = scaleOpt.length();
    const String cascadeOpt = "--cascade=";
    size_t cascadeOptLen = cascadeOpt.length();
    const String nestedCascadeOpt = "--nested-cascade";
    size_t nestedCascadeOptLen = nestedCascadeOpt.length();
    String inputName;

    CascadeClassifier cascade, nestedCascade;
    double scale = 1;

    for( int i = 1; i < argc; i++ )
    {
        if( cascadeOpt.compare( 0, cascadeOptLen, argv[i], cascadeOptLen ) == 0 )
            cascadeName.assign( argv[i] + cascadeOptLen );
        else if( nestedCascadeOpt.compare( 0, nestedCascadeOptLen, argv[i], nestedCascadeOptLen ) == 0 )
        {
            if( argv[i][nestedCascadeOpt.length()] == '=' )
                nestedCascadeName.assign( argv[i] + nestedCascadeOpt.length() + 1 );
            if( !nestedCascade.load( nestedCascadeName ) )
                cerr << "WARNING: Could not load classifier cascade for nested objects" << endl;
        }
        else if( scaleOpt.compare( 0, scaleOptLen, argv[i], scaleOptLen ) == 0 )
        {
            if( !sscanf( argv[i] + scaleOpt.length(), "%lf", &scale ) || scale < 1 )
                scale = 1;
        }
        else if( argv[i][0] == '-' )
        {
            cerr << "WARNING: Unknown option %s" << argv[i] << endl;
        }
        else
            inputName.assign( argv[i] );
    }

    if( !cascade.load( cascadeName ) )
    {
        cerr << "ERROR: Could not load classifier cascade" << endl;
        cerr << "Usage: facedetect [--cascade=\"<cascade_path>\"]\n"
            "   [--nested-cascade[=\"nested_cascade_path\"]]\n"
            "   [--scale[=<image scale>\n"
            "   [filename|camera_index]\n" ;
        return -1;
    }

    if( inputName.empty() || (isdigit(inputName.c_str()[0]) && inputName.c_str()[1] == '\0') )
        capture = cvCaptureFromCAM( inputName.empty() ? 0 : inputName.c_str()[0] - '0' );
    else if( inputName.size() )
    {
        image = imread( inputName, 1 );
        if( image.empty() )
            capture = cvCaptureFromAVI( inputName.c_str() );
    }
    else
        image = imread( "lena.jpg", 1 );

    cvNamedWindow( "result", 1 );

    if( capture )
    {
        for(;;)
        {
            IplImage* iplImg = cvQueryFrame( capture );
            frame = iplImg;
            if( frame.empty() )
                break;
            if( iplImg->origin == IPL_ORIGIN_TL )
                frame.copyTo( frameCopy );
            else
                flip( frame, frameCopy, 0 );

            detectAndDraw( frameCopy, cascade, nestedCascade, scale );

            if( waitKey( 10 ) >= 0 )
                goto _cleanup_;
        }

        waitKey(0);
_cleanup_:
        cvReleaseCapture( &capture );
    }
    else
    {
        if( !image.empty() )
        {
            detectAndDraw( image, cascade, nestedCascade, scale );
            waitKey(0);
        }
        else if( !inputName.empty() )
        {
            /* assume it is a text file containing the
            list of the image filenames to be processed - one per line */
            FILE* f = fopen( inputName.c_str(), "rt" );
            if( f )
            {
                char buf[1000+1];
                while( fgets( buf, 1000, f ) )
                {
                    int len = (int)strlen(buf), c;
                    while( len > 0 && isspace(buf[len-1]) )
                        len--;
                    buf[len] = '\0';
                    cout << "file " << buf << endl;
                    image = imread( buf, 1 );
                    if( !image.empty() )
                    {
                        detectAndDraw( image, cascade, nestedCascade, scale );
                        c = waitKey(0);
                        if( c == 27 || c == 'q' || c == 'Q' )
                            break;
                    }
                }
                fclose(f);
            }
  开发者_如何学运维      }
    }

    cvDestroyWindow("result");

    return 0;
}

The exception threw up at here:

if( !cascade.load( cascadeName ) )
{
    cerr << "ERROR: Could not load classifier cascade" << endl;
    cerr << "Usage: facedetect [--cascade=\"<cascade_path>\"]\n"
        "   [--nested-cascade[=\"nested_cascade_path\"]]\n"
        "   [--scale[=<image scale>\n"
        "   [filename|camera_index]\n" ;
    return -1;
}

The rest of the code is working. When I comment the above part up, the rest of the entire code works. The camera window opens up, although obviously the face detection does not trigger.

Can someone tell me what's going on?

EDIT: I looked at the console during the exception and found this:

OpenCV error:NULL pointer <NULL filename> in unknown function , file ..\..\..\..\ocv\opencv\src\cxcore\cxpersistence.cpp, line 2568

What is that supposed to mean?

Did you load the cascade to trigger face detection ? It seems that it cannot find the cascade path..

You need a cascade to use this face detection and write the path of this last in the command line when you run the program...

Method load() of CascadeClassifier takes a C++ std::string with the filename as input.

You are using the type String which is probably defined by Visual Studio somewhere. I'm not sure if these types are compatible, so you better stick with the one from #include <string>.

I think you should put the absolute path of the .xml file in the command line when you debug it. Because when open this kind of file a method of the standard string library is used, I think it just receive the absolute path.