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.

Please advise!
Thanks a lot

Added after 1 30 minutes:

I have tried 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

[ChrisW67]

Here is a wild guess: storage (the second argument to cvFindContours()) is null.

[YDYD]

yes, solved. Thanks.

If i want draw rectangle, cvRectangle can't use.
because the image is a QImage,
any qt command can draw rectangle?

[anda_skoa]

QPainter::drawRect().

Cheers,
_