[SOLVED][ERROR] [HELP] Using Qt + OpenCV to get what does webcam see

YDYD

I am using qt4.8 , raspbian wheezy
i get some error and i not really understand.

in dialog.ui, i just add a Label name "view" and 2 pushButton "startButton" & "stopButton"

I will post my error msg after my coding.

Please Help!
Thanks in advance.

@//cameradevice.h
#ifndef CAMERADEVICE_H
#define CAMERADEVICE_H

#include <QtCore/QObject>

QT_BEGIN_NAMESPACE
class QTimer;
class QImage;
QT_END_NAMESPACE

namespace cv{
class VideoCapture;
class Mat;
}

class CameraDevice : public QObject
{
Q_OBJECT
public:
explicit CameraDevice(QObject *parent = 0);
~CameraDevice();

signals:
void imageReady(const QImage& image);

public slots:
bool start();
bool stop();

private slots:
void onTimeout();

private:
QImage imageFromMat(const cv::Mat& frame);
cv::VideoCapture * m_capture;
QTimer * m_timer;
};

#endif // CAMERADEVICE_H@

@//cameradevice.cpp
#include <QtCore/QTimer>
#include <QtGui/QImage>
#include "opencv/cv.h"
#include "opencv/highgui.h"
#include "cameradevice.h"

CameraDevice::CameraDevice(QObject *parent) :
QObject(parent)
{
m_capture = new cv::VideoCapture;
m_timer = new QTimer(this);

connect(m_timer, SIGNAL(timeout()), this, SLOT(onTimeout()));

}

CameraDevice::~CameraDevice()
{
delete m_capture;
m_capture = NULL;
}

bool CameraDevice::start()
{
if (m_capture->isOpened()) {
return true;
}
m_capture->open(CV_CAP_ANY);
if (m_capture->isOpened()) {
m_timer->start(40);
}
return m_capture->isOpened();
}

bool CameraDevice::stop()
{
if (m_capture->isOpened()) {
m_capture->release();
}
return true;
}

void CameraDevice::onTimeout()
{
if (!m_capture->isOpened()) {
return;
}
static cv::Mat frame;
*m_capture >> frame;
if (frame.cols) {
emit imageReady(imageFromMat(frame));
}
}

QImage CameraDevice::imageFromMat(const cv::Mat &frame)
{
const unsigned char* src = frame.ptr();
QImage image(frame.cols, frame.rows, QImage::Format_RGB32);
unsigned char * des = image.bits();
unsigned long count = frame.cols * frame.rows;
for (unsigned long i = 0; i < count; ++i)
{
*des++ = *src++;
*des++ = *src++;
*des++ = *src++;
*des++ = 0xff;
}
return image;
}@

@//dialog.h
#ifndef DIALOG_H
#define DIALOG_H

#include <QtGui/QDialog>

namespace Ui {
class Dialog;
}

class CameraDevice;

class Dialog : public QDialog
{
Q_OBJECT

public:
explicit Dialog(QWidget *parent = 0);
~Dialog();

private slots:
void onImageArrival(const QImage & image);

private:
Ui::Dialog *ui;
CameraDevice * m_camera;
};

#endif // DIALOG_H@

@#include <QtCore/QThread>
#include "dialog.h"
#include "ui_dialog.h"
#include "cameradevice.h"

Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog),
m_camera(new CameraDevice)
{
ui->setupUi(this);

QThread * thread = new QThread(this);
m_camera->moveToThread(thread);
thread->start();

connect(m_camera, SIGNAL(imageReady(QImage)), this, SLOT(onImageArrival(QImage)));
connect(ui->startButton, SIGNAL(clicked()), m_camera, SLOT(start()));
connect(ui->stopButton, SIGNAL(clicked()), m_camera, SLOT(stop()));

}

Dialog::~Dialog()
{
m_camera->deleteLater();
delete ui;
}

void Dialog::onImageArrival(const QImage &image)
{
ui->view->setPixmap(QPixmap::fromImage(image));
}@

@//main.cpp
#include <QtGui/QApplication>
#include "dialog.h"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Dialog w;
w.show();

return a.exec&#40;&#41;;

}@

ERROR:
@pi@raspberrypi:~/qt/Dialog$ make
g++ -c -pipe -O2 -Wall -W -D_REENTRANT -DQT_WEBKIT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt4/mkspecs/linux-g++ -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I. -I. -o cameradevice.o cameradevice.cpp
g++ -c -pipe -O2 -Wall -W -D_REENTRANT -DQT_WEBKIT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt4/mkspecs/linux-g++ -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I. -I. -o dialog.o dialog.cpp
dialog.cpp: In constructor ‘Dialog::Dialog(QWidget*)’:
dialog.cpp:11:21: error: no matching function for call to ‘Ui::Dialog::setupUi(Dialog* const)’
dialog.cpp:11:21: note: candidate is:
ui_dialog.h:39:10: note: void Ui_Dialog::setupUi(QMainWindow*)
ui_dialog.h:39:10: note: no known conversion for argument 1 from ‘Dialog* const’ to ‘QMainWindow*’
make: *** [dialog.o] Error 1@

please help, thank you!

SGaist

Hi,

Did you start you project from a QMainWindow and then changed manually the class to a QDialog ?

YDYD

Hi.
For dialog I din change. But I change the cameradevice to QObject

SGaist

How did you create your dialog ?

YDYD

Qt GUI application. Qmainwindow

SGaist

Then how did it become a QDialog ?

YDYD

errr, I changed the QMainwindow to QDialog manually, i should use QMainwindow or QDialog to create Dialog class?

YDYD

[UPDATE]
After correction, I get another error as following:

ERROR
@pi@raspberrypi:~/qt/Dialog$ qmake -project
pi@raspberrypi:~/qt/Dialog$ qmake Dialog.pro
pi@raspberrypi:~/qt/Dialog$ make
g++ -Wl,-O1 -o Dialog cameradevice.o dialog.o main.o moc_cameradevice.o moc_dialog.o -L/usr/lib/arm-linux-gnueabihf -lQtGui -lQtCore -lpthread
cameradevice.o: In function CameraDevice::CameraDevice(QObject*)': cameradevice.cpp:(.text+0x24): undefined reference to cv::VideoCapture::VideoCapture()'
cameradevice.o: In function cv::Mat::~Mat()': cameradevice.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x70): undefined reference to cv::fastFree(void*)'
cameradevice.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x7c): undefined reference to `cv::Mat::deallocate()'
collect2: ld returned 1 exit status
make: *** [Dialog] Error 1@

Jeroentjehome

The error is because the CameraDevice class is unable to find the cv class when calling it's static member function: VideoCapture. What type of library do you include? Or do you use the QLibrary for that??

YDYD

i include

highgui
cv
cxcore

YDYD

From my knowledge,

VideoCapture is under highgui.hpp.

i have include this file already.

anyone knwo what is happening?

SGaist

You are not linking to the OpenCV libraries

YDYD

Do you mean in XXX.pro file ?

SGaist

Yes indeed, in you project pro file

YDYD

@OPENCV_PATH = /usr/local/include/opencv2/
LIBS_PATH = /usr/local/include/opencv/
LIBS += -L$$LIBS_PATH
-lcv
-lhighgui
-lcxcore

INCLUDEPATH += $$OPENCV_PATH/core
$$OPENCV_PATH/highgui/@

This is how my linking look like

SGaist

Are you sure you are linking to all the needed libraries ?

YDYD

no, i am nt sure, but i checked many times if i left out any.
Should not be left out...
if this is not left out of libraries, what is the problem ?

SGaist

Just a missing library. You can check with pkg-config what you need. You can even use it within your pro file (have a look at qmake's documentation)

YDYD

Ok. I give it a try and looh. Thx a lot SGaist

YDYD

[quote author="SGaist" date="1403731430"]Just a missing library. You can check with pkg-config what you need. You can even use it within your pro file (have a look at qmake's documentation) [/quote]

Don't really know how to do....
I just have a look at the qmake genarated makefile. The INCPATH inside should be the openCV path ? It is different.
the another thing to mention is, after i qmake project, my Dialog.pro file will changed. the coding will all replaced.

i am new to Qt and OpenCV, i just could not link them up.

Thanks to SGaist again,