How to work the loop in Qt GUI application and display the qimage

[dazzi]

I am new to Qt and OpenCV and need help with the following problem.

I am developing a code to count vehicles coming to a park. Pre-obtained input video is used to develop the algorithm. I have chosen a Qt widget application with OpenCV for this. Currently when compiling, the loop below is skipped.
@for( ; contour != 0; contour = contour->h_next )
{
bndRect = cvBoundingRect(contour, 0);
ui->txtXYnew->appendPlainText("one contour");
pt1.x = bndRect.x;
pt1.y = bndRect.y;
pt2.x = bndRect.x + bndRect.width;
pt2.y = bndRect.y + bndRect.height;
printf("--------------------\n");
cvRectangle(newImage, pt1, pt2, CV_RGB(255,0,0), 1);
}@

and the compilation moves to the next section. Why is that, am I using the timer function wrong ? (I have tested this in a console application and it worked fine both Qt and Visual Studio).

I have used two labels, one to display the input frame, and the second for the processed frame. Currently in the processed frame a black frame is shown. but it should show the processed frame with rectangles drawn around contours.

Is there any way to correct this code ? Below is the complete code.

@include "dialog.h"
#include "ui_dialog.h"
#include <QtCore>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv/cv.h>
using namespace cv;

using namespace std;

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

inputMovie = cvCaptureFromAVI("E:\pk.avi");
if (!inputMovie){
ui->txtXYnew->appendPlainText("error video");
return;
}

tmrTimer=new QTimer(this);
connect(tmrTimer,SIGNAL(timeout()),this,SLOT(processedframesandudateGUI()));
tmrTimer->start(25);
}
//////////////////////////////////////////////////////////////////////////////////
Dialog::~Dialog()
{
delete ui;
}

/////////////////////////////////////////////////////////////////////////////////
void Dialog::processedframesandudateGUI(){

CvRect bndRect = cvRect(0,0,0,0);

CvPoint pt1, pt2;


CvSize imgSize;
imgSize.width = 540;
imgSize.height = 432;

greyImage = cvCreateImage( imgSize, IPL_DEPTH_8U, 1);
movingAverage = cvCreateImage( imgSize, IPL_DEPTH_32F, 3);
colourImage = cvQueryFrame(inputMovie);

bool first = true;

    if(!colourImage)
       { ui->txtXYnew->appendPlainText("no frames");
        return;}

    if(first)
            {
                    difference = cvCloneImage(colourImage);
                    temp = cvCloneImage(colourImage);
                    cvConvertScale(colourImage, movingAverage, 1.0, 0.0);

                first = false;
            }

    cvConvertScale(movingAverage, temp, 1.0, 0.0);
    cvAbsDiff(colourImage,temp,difference);


    cvCvtColor(difference, greyImage, CV_RGB2GRAY);

    cvThreshold(greyImage,greyImage, 70, 255, CV_THRESH_BINARY);


    newImage = cvCloneImage(colourImage);

    cvDilate(greyImage, greyImage, 0, 18);
    cvErode(greyImage, greyImage, 0, 10);

   CvMemStorage* storage = cvCreateMemStorage(0);
   CvSeq* contour = 0;

     ui->txtXYnew->appendPlainText("contour");
     printf("******\n");

cvFindContours( greyImage, storage, &contour, sizeof(CvContour), CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE);

          for( ; contour != 0; contour = contour->h_next )

            {
                bndRect = cvBoundingRect(contour, 0);

                ui->txtXYnew->appendPlainText("one contour");
                pt1.x = bndRect.x;
                pt1.y = bndRect.y;
                pt2.x = bndRect.x + bndRect.width;
                pt2.y = bndRect.y + bndRect.height;

                printf("--------------------\n");
             cvRectangle(newImage, pt1, pt2, CV_RGB(255,0,0), 1);


            }

 printf("here\n");

cvCvtColor(colourImage, colourImage, CV_BGR2RGB);
QImage qimgOriginal((uchar*)colourImage->imageData,colourImage->width, colourImage->height, colourImage->widthStep, QImage::Format_RGB888);
QImage qimgProcessed((uchar*)newImage->imageData,newImage->width, newImage->height, newImage->widthStep, QImage::Format_RGB888);

ui->label->setPixmap(QPixmap::fromImage(qimgOriginal));
ui->label->resize(ui->label->pixmap()->size());
ui->txtXYnew->appendPlainText("one frame");

ui->label_2->setPixmap(QPixmap::fromImage(qimgProcessed));
ui->label_2->resize(ui->label_2->pixmap()->size());

cvReleaseImage(&temp);
cvReleaseImage(&difference);
cvReleaseImage(&greyImage);
cvReleaseImage(&movingAverage);

}

///////////////////////////////////////////////////////////////////////////////////////
void Dialog::on_pushButton_clicked()
{

if(tmrTimer->isActive()==true)
{
tmrTimer->stop();
ui->pushButton->setText("resume");
}
else
{
tmrTimer->start(25);
ui->pushButton->setText("pause");
}
}@

i changed the above code with c++ api as below and still that loop is skipped..

@ std::vector<std::vectorcv::Point > contours; // Vector for storing contour
std::vectorcv::Vec4i hierarchy;
cv::Rect rect;

//now we try to find contours on the grayscale image
findContours( greyImage, contours, hierarchy,CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE );

    for( int i = 0; i< contours.size(); i++ ) // iterate through each contour.
     {
      double a = contourArea( contours[i],false);  //  Find the area of contour

      if(a > 30)//you can delete this lines if you don't want search big contours
      {
      rect = boundingRect(contours[i]); // Find the bounding rectangle
      cv::rectangle(newImage, rect,  cv::Scalar(255,0,0),1, 8,0);//draw rect

printf("==============v======");
}
printf("=v=");
}@
any help to work the code above would be greatly appreciated. bear with me for my bad grammar. English is not my native language. god bless u all.

[dheerendra]

@for( ; contour != 0; contour = contour->h_next )@

It may not be compilation issue. It must be logic issue in the above loop. Just check it. What is the initial value of contour ? What is next value of contour. Can you just print and check them ?

[dazzi]

yes sir i printed those values

initial value of contour=0 

and when i try to print the value of contour->h_next it crashes.

i think it contains a null value. can someone correct my logic.
thanx in advance sir for your kind attention. i waited till someone reply.