OpenCV: Incorrect contour around blobs - image-processing

Question

I'm trying to draw contours around blobs in a binary image, however, sometimes, openCV draws a single contour around two distinct blobs. below is an example. How can i solve this issue?
Here it should draw two bounding boxes for the blob on the right and separately for the one of the left. I agree they are close but enough distance in between them. I'm only drawing External contours instead of the tree or list. I'm also using cvFindNextContour(contourscanner) as this is a easier implementation for my case.
Thanks
EDIT:
Image displayed in the "output" window is from a different function which does just image subtraction. Image displayed in the "contours" window is in the function pplfind(). "output" image is passed to img_con().
IplImage* img_con(IplImage* image){
int ppl;
CvMemStorage* memstr = cvCreateMemStorage();
IplImage* edges = cvCreateImage(cvGetSize(image),8,1);
cvCanny(image,edges,130,255);
CvContourScanner cscan = cvStartFindContours(image,memstr,sizeof(CvContour),CV_RETR_EXTERNAL,CV_CHAIN_APPROX_NONE,cvPoint(0,0));
ppl = pplfind(cscan,cvGetSize(image));
if (ppl !=0 )
printf("Estimated number of people: %d\n",ppl);
cvEndFindContours(&cscan);
cvClearMemStorage(memstr);
return edges;
}
int pplfind(CvContourScanner cscan, CvSize frSize){
ofstream file; char buff[50];
file.open("box.txt",ofstream::app);
int ppl =0;
CvSeq* c;
IplImage *out = cvCreateImage(frSize,8,3);
while (c = cvFindNextContour(cscan)){
CvRect box = cvBoundingRect(c,1);
if ((box.height > int(box.width*1.2))&&(box.height>20)){//&&(box.width<20)){//
ppl++;
cvRectangle(out,cvPoint(box.x,box.y),cvPoint(box.x+box.width,box.y+box.height),CV_RGB(255,0,50),1);
cvShowImage("contours",out);
//cvWaitKey();
}
//printf("Box Height: %d , Box Width: %d ,People: %d\n",box.height,box.width,ppl);
//cvWaitKey(0);
int coord = sprintf_s(buff,"%d,%d,%d\n",box.width,box.height,ppl);
file.write(buff,coord);
}
file.close();
cvReleaseImage(&out);
return ppl;
}

Answer 1

I've never used cvFindNextContour, but running cvFindContours with CV_RETR_EXTERNAL on your image seems to work fine:
I use OpenCV + Python, so this code might not be useful for you, but for the sake of completeness here it goes:
contours = cv.findContours(img, cv.CreateMemStorage(0), mode=cv.CV_RETR_EXTERNAL)
while contours:
(x,y,w,h) = cv.BoundingRect(contours)
cv.Rectangle(colorImg, (x,y), (x+w,y+h), cv.Scalar(0,255,255,255))
contours = contours.h_next()
Edit: you asked how to draw only those contours with certain properties; it would be something like this:
contours = cv.findContours(img, cv.CreateMemStorage(0), mode=cv.CV_RETR_EXTERNAL)
while contours:
(x,y,w,h) = cv.BoundingRect(contours)
if h > w*1.2 and h > 20:
cv.Rectangle(colorImg, (x,y), (x+w,y+h), cv.Scalar(0,255,255,255))
contours = contours.h_next()