Opencv and qt linux

[hezbon]

I want to start handling image processing using opencv and qt so i have downloaded the opencv 2.2.0 and extracted it.
i have included the file file paths to my .pro.
Myy question is can i use it just like qextserial or opencv sources have to be compiled?
if so why am getting error in cvReleaseCapture as undefined function.

[high_flyer]

opencv is a lib.
you have to build it, and in your Qt project add the include paths to it, and library path with opencv lib is, and link to it.

[hezbon]

opencv is a lib.
you have to build it, and in your Qt project add the include paths to it, and library path with opencv lib is, and link to it.
I have built it using Cmake and I used the Cmake-gui and then run the make and did the make install so i have the libraries built and when i try running my first program i get this error :-1: error: collect2: error: ld returned 1 exit status.
and i have given the path to my lis

#-------------------------------------------------
#
# Project created by QtCreator 2012-08-08T05:04:23
#
#-------------------------------------------------

QT += core gui

TARGET = opvc
TEMPLATE = app


INCLUDEPATH +=/usr/local/include/opencv
INCLUDEPATH +=/usr/local/include/opencv2/core
INCLUDEPATH +=/usr/local/include/opencv2/imgproc
INCLUDEPATH +=/usr/local/include/opencv2/ml
INCLUDEPATH +=/usr/local/include/opencv2/highgui
INCLUDEPATH +=/usr/bin/ld
INCLUDEPATH +=/home/oloo/Downloads/OpenCV2.4/lib
LIBS +=-L/usr/bin

LIBS += -L/usr/local/lib/libopencv_contrib.so
LIBS += -LD: /usr/local/lib
LIBS += -L/home/oloo/Downloads/OpenCV2.4/lib
SOURCES += main.cpp\
mainwindow.cpp

HEADERS += mainwindow.h

FORMS += mainwindow.ui

and this my code

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <cv.h>
#include <highgui.h>
#include <core_c.h>
#include <types_c.h>
#include <cxcore.h>
#include <ml.h>
#include <cvaux.h>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{

IplImage *img=0;
cap=cvCaptureFromCAM(0);
//cap.cvCaptureFromCAM(0);
ui->setupUi(this);

//IplImage *img=cvLoadImage("img.jpg");
//cvNamedWindow("Example1", CV_WINDOW_AUTOSIZE );
}

MainWindow::~MainWindow()
{
delete ui;
}

[high_flyer]

is /usr/local/lib/l in your LD_LIBRARY_PATH?

[hezbon]

I have added libraries and now i dont get the error but now my code cannot open my webcam

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <cv.h>
#include <highgui.h>
#include <core_c.h>
#include <types_c.h>
#include <cxcore.h>
#include <ml.h>
#include <cvaux.h>
#include <QtGui>
#include <QtDebug>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{

//IplImage *img=0;

//cap.cvCaptureFromCAM(0);
ui->setupUi(this);

IplImage *img=cvLoadImage("img.jpg");
// do{
cap=cvCaptureFromCAM(0);
// }while(!cap);

if(cap==NULL){

qDebug()<<"cannot connect"<<cvErrorStr(cvGetErrStatus());
}

cvNamedWindow("Example1", CV_WINDOW_AUTOSIZE );
}

MainWindow::~MainWindow()
{
delete ui;
}

[high_flyer]

I have added libraries and now i dont get the error but now my code cannot open my webcam
This is not a Qt issue - ask it on an openCV forum.