crash without error message opencv under Qt - c++

Question

I have a problem under Qt, Actually I want to use opencv under it (ubuntu) and there is a crash.
If I compile under the terminal :
g++ pkg-config --cflags opencv example.cc -o output_file pkg-config --libs opencv
All is all right but under QT there is a crashed problem and I just read this message error :
Starting /home/quentin/build-test_opencv-Desktop_Qt_5_2_1_GCC_64bit-Release/test_opencv...
The program has unexpectedly finished.
/home/quentin/build-test_opencv-Desktop_Qt_5_2_1_GCC_64bit-Release/test_opencv crashed
This is my .pro :
QT += core
QT -= gui
TARGET = test_opencv
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
CONFIG += link_pkgconfig
PKGCONFIG += opencv
SOURCES += main.cpp
INCLUDEPATH += -I /usr/local/include/opencv
LIBS += `pkg-config opencv --libs`
and this is my main.cpp :
#include <QCoreApplication>
#include <iostream>
#include "cv.h"
#include "highgui.h"
using namespace std;
int main(int argc, char *argv[])
{
IplImage* img = cvLoadImage( "lena.png" );
cout << "Image WIDTH = " << img->width << endl;
cout << "Image HEIGHT = " << img->height << endl;
cvReleaseImage( &img );
return 0;
}

Answer 1

Most likely cvLoadImage fails and returns nullptr. You never bother checking for that.

Answer 2

What version of openCV do you use? What berak means is that IplImage is not used in the newer versions of openCV. Use Mat instead of IplImage. Try this code and tell me what happens:
#include <QCoreApplication>
#include <iostream>
#include <stdio.h>
#include <opencv2/core/core.hpp>
#include "opencv2/highgui/highgui.hpp"
int main(int argc, char *argv[])
{
Mat* img = new cv::Mat(cv::imread("lena.png",CV_LOAD_IMAGE_COLOR));
if(img == NULL){
perror("Could not load image");
}
std::cout << "Image WIDTH = " << img->cols << std::endl;
std::cout << "Image HEIGHT = " << img->rows << std::endl;
img->release();
return 0;
}
This will work in opencv 2.4.X. Also make sure your image is in the same folder as your program. Please tell me of any error.