I get an error when compiling with the cv::imread function (very basic one) included the right files and the .pro is good:

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = OpenCVTest TEMPLATE = app

INCLUDEPATH += /home/carlos/OpenCV/opencv-2.4.9

LIBS += -L /home/carlos/OpenCV/opencv-2.4.9/build/lib/ -libopencv_core.so -llibopencv_highgui.so -llibopencv_imgproc.so -llibopencv_features2d.so -llibopencv_calib3d.so

SOURCES += main.cpp\ mainwindow.cpp

HEADERS += mainwindow.h

FORMS += mainwindow.ui

My main file is this:

include "mainwindow.h"

include "QApplication"

include "include/opencv/highgui.h"

include "modules/core/include/opencv2/core/core.hpp"

include "modules/highgui/include/opencv2/highgui/highgui.hpp"

using namespace std;

using namespace cv;

int main(int argc, char *argv[]){

QApplication a(argc, argv);
MainWindow w;
w.show();

Mat image = cv::imread("descarga.jpg",0);
namedWindow("My Image");
imshow("My Image", image);
waitKey(5000);

return a.exec();

}

The error is:

/home/carlos/Programing/OpenCVTest/main.cpp:16: error: undefined reference to `cv::imread(std::string const&, int)'

I think is well implemented, is something wrong with code or it's just that it has changed for OpenCV 2.4.9?