Question

I am using the following code from the samples folder of OpenCV for face-detection in a video:

#include "stdafx.h"
#include "opencv2/objdetect/objdetect.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>

using namespace std;
using namespace cv;

/** Function Headers */
void detectAndDisplay( Mat frame );

/** Global variables */
String face_cascade_name = "lbpcascade_frontalface.xml";
String eyes_cascade_name = "haarcascade_eye_tree_eyeglasses.xml";
CascadeClassifier face_cascade;
CascadeClassifier eyes_cascade;
string window_name = "Capture - Face detection";

RNG rng(12345);

/**
 * @function main
 */
int main( int argc, const char** argv )
{
  CvCapture* capture;
  Mat frame;

  //-- 1. Load the cascade
  if( !face_cascade.load( face_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };
  if( !eyes_cascade.load( eyes_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };

  //-- 2. Read the video stream
  capture = cvCaptureFromCAM(0);
  if( capture )
  {
    while( true )
    {
      frame = cvQueryFrame( capture );

      //-- 3. Apply the classifier to the frame
      if( !frame.empty() )
       { detectAndDisplay( frame ); }
      else
       { printf(" --(!) No captured frame -- Break!"); break; }

      int c = waitKey(10);
      if( (char)c == 'c' ) { break; } 

    }
  }
  return 0;
}

/**
 * @function detectAndDisplay
 */
void detectAndDisplay( Mat frame )
{
   std::vector<Rect> faces;
   Mat frame_gray;

   cvtColor( frame, frame_gray, CV_BGR2GRAY );
   equalizeHist( frame_gray, frame_gray );

   //-- Detect faces
   face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2, 0, Size(80, 80) );

   for( int i = 0; i < faces.size(); i++ )
    {
      Mat faceROI = frame_gray( faces[i] );
      std::vector<Rect> eyes;

      //-- In each face, detect eyes
      eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CV_HAAR_SCALE_IMAGE, Size(30, 30) );
      if( eyes.size() == 2)
      {
         //-- Draw the face
         Point center( faces[i].x + faces[i].width*0.5, faces[i].y + faces[i].height*0.5 );
         ellipse( frame, center, Size( faces[i].width*0.5, faces[i].height*0.5), 0, 0, 360, Scalar( 255, 0, 0 ), 2, 8, 0 );

     for( int j = 0; j < eyes.size(); j++ )
      { //-- Draw the eyes
        Point center( faces[i].x + eyes[j].x + eyes[j].width*0.5, faces[i].y + eyes[j].y + eyes[j].height*0.5 ); 
            int radius = cvRound( (eyes[j].width + eyes[j].height)*0.25 );
            circle( frame, center, radius, Scalar( 255, 0, 255 ), 3, 8, 0 );
          }
       }

    } 
   //-- Show what you got
   imshow( window_name, frame );
}

I have OpenCV 2.4.2 working fine on my computer as I’ve tried other simple examples and they work fine. However when I try this code, it builds fine. However when I run it, I get an exception unhandled error:

Unhandled exception at 0x000007FEEF848158 (opencv_objdetect242.dll) in OpenCVTest2.exe: 0xC0000005: Access violation reading location 0x0000000000000010.

I tried stepping into the code line by line, and the exception is invoked when I get to the line:

if( !eyes_cascade.load( eyes_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };

I have included the xml classifier files in my visual studio project.

Am I doing something wrong? Or is this a problem in general with using the face detection sample on Windows as mentioned in some of the comments to this question?

Answer 1

I think I got it working by referring to some sample code provided in the OpenCV installation package. I’ve pasted the code here for anyone who stumbles across this in the future.