Error while detecting faces and apply blur on them - c++

Question

I'm creating an application that capture video stream via webcam and detect the faces and blur them
And this is my code
#include <iostream>
#include <vector>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/features2d/features2d.hpp>
#include <opencv2/objdetect/objdetect.hpp>
using namespace std;
using namespace cv;
int blur_value = 50;
Mat src; Mat dst;
int main(int argc, char* argv[])
{
VideoCapture cap(0);
bool read = true;
char winName[] = "Blured WebCam";
String face_cascade_name = "haarcascade_frontalface_alt.xml";
CascadeClassifier face_cascade;
if(!cap.isOpened())
{
cout<<"Error while opening your webcam\n";
return 0;
}
for(;;)
{
cap.read(src);
vector <Rect> faces;
Mat blk;
cvtColor( src, blk, COLOR_BGR2GRAY );
equalizeHist( blk, blk );
face_cascade.detectMultiScale( blk, faces, 1.1, 2, 0|CV_HAAR_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 );
blur( src, dst, Size( faces[i].width/2, faces[i].height/2), Point(-1,-1) );
}
imshow(winName, dst);
switch(waitKey(10))
{
case 27:
return 0;
}
}
return 0;
}
There is no errors in the compilation process, the error comes in when i try to run the application
I got this error
OpenCV Error: Assertion failed (size.width>0 && size.height>0) in
imshow, file
/build/opencv-SviWsf/opencv-2.4.9.1+dfsg/modules/highgui/src/window.cpp,
line 269 terminate called after throwing an instance of
'cv::Exception' what():
/build/opencv-SviWsf/opencv-2.4.9.1+dfsg/modules/highgui/src/window.cpp:269:
error: (-215) size.width>0 && size.height>0 in function imshow
Aborted (core dumped)
Where is the problem?

Answer 1

You are probably getting that error when there are no faces detected. If imshow is called on empty frame, it'll give an error. Try this as #miki has suggested
if(!faces.empty()) {
imshow(winName, dst);
}