How to find a color contours after convert img to black and white??

YDYD

Hi all,

I have already converted the img to black and white,

i would like to find the contours and use a rectangle frame to show frame the wanted part.
I am not sure how to achieve in Qt.

I have tried using opencv, but fail, code as following

@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));

unsigned char *data_hsv= (unsigned char*)imgHSV->imageData;
int step_hsv = imgHSV->widthStep/sizeof(unsigned char), chanels_hsv=imgHSV->nChannels;
cvFindContours(imgFilter, storage, &contour, sizeof(CvContour), CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE,cvPoint(0,0));

    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);
            H = data_hsv[step_hsv*pt->y+chanels_hsv*pt->x+0];
            S = data_hsv[step_hsv*pt->y+chanels_hsv*pt->x+1];
            V = data_hsv[step_hsv*pt->y+chanels_hsv*pt->x+2];
            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()))
        {
            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;
              }
            }
        }
    }

cvReleaseImage(&imgFilter);
cvReleaseImage(&imgHSV);

}
@

ERROR:
@OpenCV Error: Null pointer () in cvStartFindContours, file /home/pi/OpenCV-2.4.2/modules/imgproc/src/contours.cpp, line 187

terminate called after throwing an instance of 'cv::Exception'

what(): /home/pi/OpenCV-2.4.2/modules/imgproc/src/contours.cpp:187: error: (-27) in function cvStartFindContours

The program has unexpectedly finished.

/home/pi/qt/getCam/getCam exited with code 0@

Please advise!
Thanks a lot

andreyc

[quote]OpenCV Error: Null pointer () in cvStartFindContours, file /home/pi/OpenCV-2.4.2/modules/imgproc/src/contours.cpp, line 187[/quote]

According to "contours.cpp:187":https://github.com/Itseez/opencv/blob/master/modules/imgproc/src/contours.cpp#L187 your storage variable is nullptr

I don't see where you declare/allocate this variable so make sure you do it right.

YDYD

hi , thanks a lot!
when i draw rectangle,
I get weird value of my cvpoint() value, i also not sure what is the problem.