visual c++ - OpenCV Object detection tutorial

Question

I'm new to OpenCV platform. I've installed and successfully run some tutorial codes(inbuilt). But I'm facing some issues with the codes involving haarcascade.The code builds perfectly and also the webcam seems to flash light and work but the code displays blank window as attached.image

Can anyone suggest some rectification for the problem?

(I'm using opencv version 3.0.0 and Visual Studios 2013.)

    #include "stdafx.h"
    #include "opencv2/objdetect.hpp"
    #include "opencv2/videoio.hpp"
    #include "opencv2/highgui.hpp"
    #include "opencv2/imgproc.hpp"

    #include <iostream>
    #include <stdio.h>
    using namespace std;
    using namespace cv;

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

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

   /** @function main */
   int main( void )
    {
    VideoCapture capture;
Mat frame;

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

//-- 2. Read the video stream
capture.open( -1 );
if ( ! capture.isOpened() ) { printf("--(!)Error opening video capture
"); return -1; }

while ( capture.read(frame) )
{
    if( frame.empty() )
    {
        printf(" --(!) No captured frame -- Break!");
        break;
    }

    //-- 3. Apply the classifier to the frame
    detectAndDisplay( frame );

    int c = waitKey(10);
    if( (char)c == 27 ) { break; } // escape
}
return 0;
    }

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

cvtColor( frame, frame_gray, COLOR_BGR2GRAY );
equalizeHist( frame_gray, frame_gray );

//-- Detect faces
face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2, 0|CASCADE_SCALE_IMAGE, Size(30, 30) );

for ( size_t i = 0; i < faces.size(); i++ )
{
    Point center( faces[i].x + faces[i].width/2, faces[i].y + faces[i].height/2 );
    ellipse( frame, center, Size( faces[i].width/2, faces[i].height/2 ), 0, 0, 360, Scalar( 255, 0, 255 ), 4, 8, 0 );

    Mat faceROI = frame_gray( faces[i] );
    std::vector<Rect> eyes;

    //-- In each face, detect eyes
    eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CASCADE_SCALE_IMAGE, Size(30, 30) );

    for ( size_t j = 0; j < eyes.size(); j++ )
    {
        Point eye_center( faces[i].x + eyes[j].x + eyes[j].width/2, faces[i].y + eyes[j].y + eyes[j].height/2 );
        int radius = cvRound( (eyes[j].width + eyes[j].height)*0.25 );
        circle( frame, eye_center, radius, Scalar( 255, 0, 0 ), 4, 8, 0 );
    }
}
//-- Show what you got
imshow( window_name, frame );
    }

Answer 1

i think it is a known bug

could you try my updated code ( i pointed out the changes by comments)

#include "opencv2/objdetect.hpp"
#include "opencv2/videoio.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <opencv2/core/ocl.hpp> // additional header ************************

#include <iostream>
#include <stdio.h>

using namespace std;
using namespace cv;

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

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

/** @function main */
int main( void )
{
    ocl::setUseOpenCL(false); // disable OpenCL *******************
    VideoCapture capture;
    Mat frame;

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

    //-- 2. Read the video stream
    capture.open( 0 ); // Open webcam 0 ***************************
    if ( ! capture.isOpened() ) { printf("--(!)Error opening video capture
"); return -1; }

    while ( capture.read(frame) )
    {
        if( frame.empty() )
        {
            printf(" --(!) No captured frame -- Break!");
            break;
        }

        //-- 3. Apply the classifier to the frame
        detectAndDisplay( frame );

        int c = waitKey(10);
        if( (char)c == 27 ) { break; } // escape
    }
    return 0;
}

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

    cvtColor( frame, frame_gray, COLOR_BGR2GRAY );
    equalizeHist( frame_gray, frame_gray );

    //-- Detect faces
    face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2, 0|CASCADE_SCALE_IMAGE, Size(30, 30) );

    for ( size_t i = 0; i < faces.size(); i++ )
    {
        Point center( faces[i].x + faces[i].width/2, faces[i].y + faces[i].height/2 );
        ellipse( frame, center, Size( faces[i].width/2, faces[i].height/2 ), 0, 0, 360, Scalar( 255, 0, 255 ), 4, 8, 0 );

        Mat faceROI = frame_gray( faces[i] );
        std::vector<Rect> eyes;

        //-- In each face, detect eyes
        eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CASCADE_SCALE_IMAGE, Size(30, 30) );

        for ( size_t j = 0; j < eyes.size(); j++ )
        {
            Point eye_center( faces[i].x + eyes[j].x + eyes[j].width/2, faces[i].y + eyes[j].y + eyes[j].height/2 );
            int radius = cvRound( (eyes[j].width + eyes[j].height)*0.25 );
            circle( frame, eye_center, radius, Scalar( 255, 0, 0 ), 4, 8, 0 );
        }
    }
    //-- Show what you got
    imshow( window_name, frame );
}