face detection sample code for OpenCV

main.cpp

#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <opencv/ml.h>

void doMosaic(IplImage* in, int x, int y,
              int width, int height, int size);

int main (int argc, char **argv)
{
  int i, c;
  IplImage *src_img = 0, *src_gray = 0;
  const char *cascade_name = "/opt/local/share/opencv/haarcascades/haarcascade_frontalface_default.xml";
  CvHaarClassifierCascade *cascade = 0;
  CvMemStorage *storage = 0;
  CvSeq *faces;
  
  cascade = (CvHaarClassifierCascade *) cvLoad (cascade_name, 0, 0, 0);
  cvNamedWindow ("Capture", CV_WINDOW_AUTOSIZE);
  CvCapture *capture = cvCreateCameraCapture(0);
  assert(capture != NULL);
  
  while (1) {
    src_img = cvQueryFrame (capture);
    src_gray = cvCreateImage (cvGetSize(src_img), IPL_DEPTH_8U, 1);
    
    storage = cvCreateMemStorage (0);
    cvClearMemStorage (storage);
    cvCvtColor (src_img, src_gray, CV_BGR2GRAY);
    cvEqualizeHist (src_gray, src_gray);
    
    faces = cvHaarDetectObjects (src_gray, cascade, storage,
                                 1.11, 4, 0, cvSize (40, 40));
    for (i = 0; i < (faces ? faces->total : 0); i++) {
      CvRect *r = (CvRect *) cvGetSeqElem (faces, i);
      doMosaic(src_img, r->x, r->y, r->width, r->height, 20);
    }
    
    cvShowImage("Capture", src_img);
    cvReleaseImage(&src_gray);
    
    c = cvWaitKey (2);
    if (c == '\x1b')
      break;
  }
  
  cvReleaseCapture (&capture);
  cvDestroyWindow ("Capture");
  
  return 0;
}

void doMosaic(IplImage* in, int x0, int y0,
              int width, int height, int size)
{
  int b, g, r, col, row;
  
  int xMin = size*(int)floor((double)x0/size);
  int yMin = size*(int)floor((double)y0/size);
  int xMax = size*(int)ceil((double)(x0+width)/size);
  int yMax = size*(int)ceil((double)(y0+height)/size);
  
  for(int y=yMin; y<yMax; y+=size){
    for(int x=xMin; x<xMax; x+=size){
      b = g = r = 0;
      for(int i=0; i<size; i++){
        if( y+i > in->height ){
          break;
        }
        row = i;
        for(int j=0; j<size; j++){
          if( x+j > in->width ){
            break;
          }
          b += (unsigned char)in->imageData[in->widthStep*(y+i)+(x+j)*3];
          g += (unsigned char)in->imageData[in->widthStep*(y+i)+(x+j)*3+1];
          r += (unsigned char)in->imageData[in->widthStep*(y+i)+(x+j)*3+2];
          col = j;
        }
      }
      row++;
      col++;
      for(int i=0;i<row;i++){
        for(int j=0;j<col;j++){
          in->imageData[in->widthStep*(y+i)+(x+j)*3]   = cvRound((double)b/(row*col));
          in->imageData[in->widthStep*(y+i)+(x+j)*3+1] = cvRound((double)g/(row*col));
          in->imageData[in->widthStep*(y+i)+(x+j)*3+2] = cvRound((double)r/(row*col));
        }
      }
    }
  }
}

Hi anujtripathi04,

I am getting the same issue , can you please tell how you resolved this issue.

OpenCV Error: Null pointer (Invalid classifier cascade) in cvHaarDetectObjectsForROC, file /build/buildd/opencv-2.4.8+dfsg1/modules/objdetect/src/haar.cpp, line 1514
terminate called after throwing an instance of 'cv::Exception'
what(): /build/buildd/opencv-2.4.8+dfsg1/modules/objdetect/src/haar.cpp:1514: error: (-27) Invalid classifier cascade in function cvHaarDetectObjectsForROC
Regards
Simarjeet Singh