How to get specific point and draw Rectangle on QImage?

Hi all ,

I am currently working on robot vision system,

I would like to track something using Rasp-pi with Webcam.

After i process my image, i would like to box the part i needed ask the pic shown,

How can i do to achieve this? Attachment 10518

Would like to rectangle the biggest part.

I did use opencv libs to find contours and get cvpoint, but i cant get exactly what i want.

please advise

Thanks in advance

Quote:

---

I did use opencv libs to find contours and get cvpoint, but i cant get exactly what i want.

---

Can you show us your code ?

Quote:

---

i would like to box the part i needed ask the pic shown,

---

Do you want to copy a sub-region of image ? For QImages, use QImage::copy() method. For OpenCV, it depends - if you are using C++ interface, use OpenCV::Mat::copyTo method, and for C interface you can set ROI on source image (cvSetImageROI) and copy with cvCopy function.

Code:

---

void Dialog::createCam()
{
    timer = new QTimer(this);
    cam = cvCaptureFromCAM(-1);
    if(cam==NULL)
        qDebug()<<"Error: No Camera Detect.";
 
    timer->start(33);
    connect(timer,SIGNAL(timeout()),this,SLOT(getFrame()));
    connect(timer,SIGNAL(timeout()),this,SLOT(prcFrame()));
}
 
void Dialog::getFrame()
{
    frame = cvQueryFrame(cam); //get what camera see
    image = QImage ((const uchar*)frame->imageData,frame->width,frame->height,QImage::Format_RGB888).rgbSwapped();//rgbSwapped() make color better
 
    qPainter = new QPainter(&image);// all qPainter to draw rectangle on original image according to point get from Filter image
    qPainter->begin(this);
    qPainter->setPen(QPen(Qt::red,3,Qt::SolidLine));
    qPainter->drawRect(rect.x,rect.y,rect.x+rect.width,rect.y+rect.height);
    qPainter->end();
    ui->original->setPixmap(QPixmap::fromImage(image));
 
}
 
void Dialog::prcFrame()
{
    imgHSV= cvCloneImage(frame);
    cvCvtColor(frame,imgHSV,CV_BGR2HSV);
    imgFilter= cvCreateImage(cvSize(frame->width,frame->height),IPL_DEPTH_8U,1);
    cvInRangeS(imgHSV,cvScalar(ui->hueSlide1->value(),ui->satSlide1->value(),ui->lumSlide1->value(),0),cvScalar(ui->hueSlide2->value(),ui->satSlide2->value(),ui->lumSlide2->value(),0),imgFilter);
    QImage imgThresdhed = QImage ((const uchar*)imgFilter->imageData,imgFilter->width,imgFilter->height,QImage::Format_Indexed8).rgbSwapped();
    ui->filter->setPixmap(QPixmap::fromImage(imgThresdhed)); //convert to QImage and show as Filter image
 
    unsigned char *data_hsv= (unsigned char*)imgHSV->imageData;
    int step_hsv = imgHSV->widthStep/sizeof(unsigned char), chanels_hsv=imgHSV->nChannels;
    storage=cvCreateMemStorage(0);
 
    cvFindContours(imgFilter, storage, &contour, sizeof(CvContour), CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE,cvPoint(0,0)); //FindContours
 
        for(;contour;contour = contour->h_next)
        {
            area1=fabs(cvContourArea(contour,CV_WHOLE_SEQ,1 ));
 
            if(area1<100 || area1>50000 )
            {
                cvSeqRemove(contour,0);
                continue;
            }
 
            total =0;
            total_S=0;
            total_V=0;
 
            for(l = 0;l<contour->total;++l)
            {
                pt = (CvPoint *)cvGetSeqElem(contour,l);
                qDebug()<<"pt"<<pt;
                H = data_hsv[step_hsv*pt->y+chanels_hsv*pt->x+0];
                qDebug()<<"H"<<H;
                S = data_hsv[step_hsv*pt->y+chanels_hsv*pt->x+1];
                qDebug()<<"S"<<S;
                V = data_hsv[step_hsv*pt->y+chanels_hsv*pt->x+2];
                qDebug()<<"V"<<V;
                total = H + total;
                total_S= S + total_S;
                total_V= V + total_V;
            }
 
            avg = total / (contour->total);
            avg_S=total_S / (contour->total);
            avg_V=total_V / (contour->total);
 
            if((avg>=ui->hueSlide1->value())&&(avg<=ui->hueSlide2->value())&&(avg_S>=ui->satSlide1->value())&&(avg_S<=ui->satSlide2->value())&&(avg_V>=ui->lumSlide1->value())&&(avg_V<=ui->lumSlide2->value())) // compare contours size
            {
                for(i = N-1; i >= 0; --i)
                {
                  if(area1 > maxArea1[i])
                  {
                    maxArea1[i] = area1;
                    contours1[i] = contour;
                    for(m = (i-1); m >= 0; --m)
                    {
                       if(maxArea1[m] < maxArea1[m+1])
                       {
                         tmp_area1 = maxArea1[m+1];
                         tmp_cont = contours1[m+1];
                         maxArea1[m+1] = maxArea1[m];
                         contours1[m+1] = contours1[m];
                         maxArea1[m] = tmp_area1;
                         contours1[m] = tmp_cont;
                        }
                    }
                  break;
                  }
                }
            }
        }
       rect = ((CvContour*)contours1[0])->rect; //rect point
 
 
        cvReleaseMemStorage(&storage);
        cvReleaseImage(&imgFilter);
        cvReleaseImage(&imgHSV);
}

---

Can you explain what you mean by "i would like to box the part i needed ask the pic shown," ?
If I'm correct, it looks like you want to draw a bounding box around the contours with the largest area, but I can only guess. Have you verified your sorting procedure ?

Quote:

---

Originally Posted by stampede

Can you explain what you mean by "i would like to box the part i needed ask the pic shown," ?
If I'm correct, it looks like you want to draw a bounding box around the contours with the largest area, but I can only guess. Have you verified your sorting procedure ?

---

Yes，exactly [want to draw a bounding box around the contours with the largest area].

What do you mean by verified my sorting?
Do you mean the sorting of all the function?

Quote:

---

What do you mean by verified my sorting?

---

It can't be more clear - have you checked that the list is sorted after the sorting code :)