Error while opening a video with OpenCV and Qt - c++

Question

I have about 15 errors, when I want to get a video capture to view it frame by frame in an image.
First I call my video from my link.
Then get from it my frame.
Then convert it into image.
Finally view it in pixmap.
MY CODE
#include "form1.h"
#include "ui_form1.h"
#include <QtCore>
#include <QtGui>
#include <QGraphicsAnchorLayout>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsWidget>
#include "qimage.h"
#include <QFileDialog>
#include <QPixmap>
#include "qpixmap.h"
Form1::Form1(QWidget *parent) :
QDialog(parent),
ui(new Ui::Form1)
{
ui->setupUi(this);
video->open("D:/Downloads/DirectX/Zlatan Ibrahimovic ● Taekwondo Goals.mp4");
timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(updatePicture()));
timer->start(20);
}
QString fileName;
QImage Form1::getQImageFromFrame(cv::Mat frame) {
//converts the color model of the image from RGB to BGR because OpenCV uses BGR
cv::cvtColor(frame, frame, CV_RGB2BGR);
return QImage((uchar*) (frame.data), frame.cols, frame.rows, frame.step, QImage::Format_RGB888);
}
Form1::~Form1()
{
delete ui;
}
void Form1::updatePicture()
{
cv::Mat frame1;
video->operator >>( frame1);
img = getQImageFromFrame(frame1);
ui->label->setPixmap(QPixmap::fromImage(img));
}
void Form1::on_pushButton_clicked()
{
//fileName = QFileDialog::getOpenFileName(this,
//tr("Open Image"), "/elhandasya/Desktop", tr("Image Files (*.png *.jpg *.bmp)"));
//QPixmap pix(fileName);
}
'
The errors like this:
undefined reference to `cv::Mat::Mat()
D:\ubunto\QT5\Tools\QtCreator\bin\Video_Player-build-Desktop_Qt_5_0_1_MinGW_32bit-Debug\debug\form1.o:-1: In function `ZN5Form1D2Ev'
My LIBS
#-------------------------------------------------
#
# Project created by QtCreator 2013-12-16T09:23:28
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = Video_Player
TEMPLATE = app
SOURCES += main.cpp\
form1.cpp
HEADERS += form1.h
FORMS += form1.ui
INCLUDEPATH += -I"D:/ubunto/OpenCV/opencv/build/include/opencv2/imgproc"
INCLUDEPATH += -I"D:/ubunto/OpenCV/opencv/build/include/"
#INCLUDEPATH += "D:/ubunto/OpenCV/opencv/build/include/"
LIBS += -LD:/ubunto/OpenCV/opencv/build/x86/mingw/bin
-lopencv_core
-lopencv_imgproc
-lopencv_highgui
-lopencv_legacy
-lopencv_gpu
-lopencv_video
-lopencv_ml
-lopencv_contrib
#LIBS += D:\ubunto\emgu\emgucv-windows-x86 2.4.0.1717\lib
#-opencv_calib3d240
#-opencv_videostab240
#-opencv_calib3d240
#-opencv_contrib240
#-opencv_core240
#-opencv_features2d240
#-opencv_flann240
#-opencv_gpu240
#-opencv_highgui240
#-opencv_imgproc240
#-opencv_legacy240
#-opencv_ml240
#-opencv_nonfree240
#-opencv_objdetect240
#-opencv_photo240
#-opencv_stitching240
#-opencv_video240

Answer 1

If you take a look at the source code of cvVideo (an application that shows how to create a Qt window to display videos loaded with OpenCV) you can see how to achieve what you are looking for.
cvVideo.pro:
TEMPLATE = app
QT += core gui
contains(QT_VERSION, ^5\\.[0-8]\\..*) {
message("* Using Qt $${QT_VERSION}.")
QT += widgets
# On my system I have to specify g++ as compiler else it will use clang++ by default
#QMAKE_CXX=g++
#QMAKE_CC=gcc
}
HEADERS += \
cvWindow.h
SOURCES += \
main.cpp \
cvWindow.cpp
## OpenCV settings for Unix/Linux
unix:!mac {
message("* Using settings for Unix/Linux.")
INCLUDEPATH += /usr/local/include/opencv
LIBS += -L/usr/local/lib/ \
-lopencv_core \
-lopencv_highgui \
-lopencv_imgproc
}
## OpenCV settings for Mac OS X
macx {
message("* Using settings for Mac OS X.")
INCLUDEPATH += /usr/local/include/opencv
LIBS += -L/usr/local/lib/ \
-lopencv_core \
-lopencv_highgui \
-lopencv_imgproc
}
## OpenCV settings for Windows and OpenCV 2.4.2
win32 {
message("* Using settings for Windows.")
INCLUDEPATH += "C:\\opencv\\build\\include" \
"C:\\opencv\\build\\include\\opencv" \
"C:\\opencv\\build\\include\\opencv2"
LIBS += -L"C:\\opencv\\build\\x86\\vc10\\lib" \
-lopencv_core242 \
-lopencv_highgui242 \
-lopencv_imgproc242
}
# Runs this app automatically after the building has succeeded
#QMAKE_POST_LINK=./$$TARGET

Answer 2

Error tells you that you have to link, in you makefile, the specific library that include Mat:
-lopencv_core
Take a look at the documentaion.
When there are errors like:
In function `ZN5Form1D2Ev'
It could be that you have two different opencv version installed, isn't it?