Codice (dalla documentazione OpenCV)
#define CV_SEQUENCE_FIELDS() \
         int flags; /* micsellaneous flags */ \ 
         int header_size; /* size of sequence header */ \ 
         struct CvSeq* h_prev; /* previous sequence */ \ 
         struct CvSeq* h_next; /* next sequence */ \ 
         struct CvSeq* v_prev; /* 2nd previous sequence */ \ 
         struct CvSeq* v_next; /* 2nd next sequence */ \ 
         int total; /* total number of elements */ \
         int elem_size;/* size of sequence element in bytes */ \ 
         char* block_max;/* maximal bound of the last block */ \ 
         char* ptr; /* current write pointer */ \
         int delta_elems; /* how many elements allocated when the sequence grows (sequence granularity) */ \ 
         CvMemStorage* storage; /* where the seq is stored */ \ 
         CvSeqBlock* free_blocks; /* free blocks list */ \ 
         CvSeqBlock* first; /* pointer to the first sequence block */
 
 
 typedef struct CvSeq 
 { 
      CV_SEQUENCE_FIELDS() 
 } CvSeq;
 

Codice (dalla documentazione OpenCV)
#include "stdio.h"
#include "cv.h"
#include "highgui.h"
 
int main( int argc, char* argv[] )
{
	IplImage* img = cvCreateImage( cvSize( 640, 480),8, 1 );
	cvSet( img, cvScalarAll(0) );
	IplImage* res = cvCreateImage( cvSize(640,480), 8, 3 );
	cvSetZero( res );
 
	// -----> Disegno di due bersagli da analizzare contenuti in un rettangolo
	cvRectangle( img, cvPoint(30,30), cvPoint(630,440), CV_RGB(255,255,255), -1 );
 
	cvCircle( img, cvPoint( 200,200), 120, CV_RGB(150,150,150), -1 );
	cvCircle( img, cvPoint( 200,200), 80, CV_RGB(100,100,100), -1 );
	cvCircle( img, cvPoint( 200,200), 40, CV_RGB(50,50,50), -1 );
	cvCircle( img, cvPoint( 200,200), 10, CV_RGB(10,10,10), -1 );
 
	cvCircle( img, cvPoint( 480,300), 120, CV_RGB(150,150,150), -1 );
	cvCircle( img, cvPoint( 480,300), 80, CV_RGB(100,100,100), -1 );
	cvCircle( img, cvPoint( 480,300), 40, CV_RGB(50,50,50), -1 );
	cvCircle( img, cvPoint( 480,300), 10, CV_RGB(10,10,10), -1 );
	// <----- Disegno di due bersagli da analizzare  contenuti in un rettangolo
 
 
	cvNamedWindow( "Originale" );
	cvShowImage( "Originale", img ); 
 
	cvNamedWindow( "Risultato" );
 
	// Evidenziazione dei contorni
	cvCanny( img, img, 5, 90 );
 
	cvNamedWindow( "Canny" );
	cvShowImage( "Canny", img );
 
	// Espansione dei contorni in modo da analizzarli in modo "utile"
	// (Provate a vedere cosa succede commentando la riga successiva)
	cvDilate( img, img, NULL, 1 );
 
	cvNamedWindow( "Canny dilated" );
	cvShowImage( "Canny dilated", img );
 
	CvMemStorage* storage = cvCreateMemStorage( 0);
	CvSeq* contours=NULL;
	int contour_num;
 
	// Analisi dei contorni
	contour_num = cvFindContours( img, storage, &contours, sizeof(CvContour), 
		CV_RETR_TREE, CV_CHAIN_APPROX_NONE );
 
	printf( "Trovati %d contorni\r\n", contour_num );
 
	CvSeq* succ = contours;
 
	int cont=0;
 
	while( succ!=NULL )
	{
		cvDrawContours( res, succ, CV_RGB(255,0,0), CV_RGB(255,0,0), 0, -1 );
		cont++;
 
		cvShowImage( "Risultato", res );
		cvWaitKey(0);
 
		CvSeq* hole_0 = succ->v_next;
		while( hole_0!=NULL )
		{
			cvDrawContours( res, hole_0, CV_RGB(0,255,0), CV_RGB(0,255,0),0, -1 );
			cont++;
 
			cvShowImage( "Risultato", res ); 
			cvWaitKey(0);
 
			CvSeq* hole_1 = hole_0->v_next;
			while( hole_1!=NULL )
			{
				cvDrawContours( res, hole_1, CV_RGB(0,0,255), CV_RGB(0,0,255), 0, -1 );
				cont++;
 
				cvShowImage( "Risultato", res ); 
				cvWaitKey(0);
 
				CvSeq* hole_2 = hole_1->v_next;
				while( hole_2!=NULL )
				{
					cvDrawContours( res, hole_2, CV_RGB(0,255,255), CV_RGB(0,255,255), 0, -1 );
					cont++;
 
					cvShowImage( "Risultato", res );
					cvWaitKey(0);
 
					CvSeq* hole_3 = hole_2->v_next;
					while( hole_3!=NULL )
					{
						cvDrawContours( res, hole_3, CV_RGB(255,255,0), CV_RGB(255,255,0), 0, -1 );
						cont++;
 
						cvShowImage( "Risultato", res );
						cvWaitKey(0);
 
						CvSeq* hole_4 = hole_3->v_next;
						while( hole_4!=NULL )
						{
							cvDrawContours( res, hole_4, CV_RGB(255,0,255), CV_RGB(255,0,255), 0, -1 );
							cont++;
 
							cvShowImage( "Risultato", res ); 
							cvWaitKey(0);
 
							CvSeq* hole_5 = hole_4->v_next;
							while( hole_5!=NULL )
							{
								cvDrawContours( res, hole_5, CV_RGB(255,255,255), CV_RGB(255,255,255), 0, -1 );
								cont++;
 
								cvShowImage( "Risultato", res ); 
								cvWaitKey(0);
 
 
								CvSeq* hole_6 = hole_5->v_next;
								while( hole_6!=NULL )
								{
									cvDrawContours( res, hole_6, CV_RGB(100,100,100), CV_RGB(100,100,100), 0, -1 );
									cont++;
 
									cvShowImage( "Risultato", res );
									cvWaitKey(0);
 
 
									CvSeq* hole_7 = hole_6->v_next;
									while( hole_7!=NULL )
									{
										cvDrawContours( res, hole_7, CV_RGB(0,0,0), CV_RGB(0,0,0), 0, -1 );
										cont++;
 
										cvShowImage( "Risultato", res ); 
										cvWaitKey(0);
 
 
										CvSeq* hole_8 = hole_7->v_next;
										while( hole_8!=NULL )
										{
											cvDrawContours( res, hole_8, CV_RGB(200,200,200), CV_RGB(200,200,200), 0, -1 );
											cont++;
 
											cvShowImage( "Risultato", res );
											cvWaitKey(0);
 
											hole_8 = hole_8->h_next;
										}
 
										hole_7 = hole_7->h_next;
									}
 
									hole_6 = hole_6->h_next;
								}
 
								hole_5 = hole_5->h_next;
							}
 
							hole_4 = hole_4->h_next;
						}
 
						hole_3 = hole_3->h_next;
					}
 
					hole_2 = hole_2->h_next;
				}
 
				hole_1 = hole_1->h_next;
			}
 
			hole_0 = hole_0->h_next;
		}
 
		succ = succ->h_next;
	}
 
	printf( "Disegnati %d contorni\r\n", cont );
 
	// Alla fine
	printf( "\r\nPremi un tasto per terminare..." );
	cvWaitKey(0);
 
	cvReleaseImage( &img );
	cvReleaseImage( &res );
	cvReleaseMemStorage( &storage );
	cvDestroyAllWindows();
 
	return 0;
}
 

  root (succ rosso)
  |
  |
  succ->v_next (hole_0 verde)
  |
  ___________________________________
  |                                                  |
  hole_0->v_next (hole_1 blu)          hole_0->h_next (hole_1 blu)
  |                                                  |
  |                                                  |
  hole_1->v_next (hole_2 ciano)        hole_1->v_next (hole_2 ciano)
  |                                                  |
  |                                                  |
  hole_2->v_next (hole_3 giallo)       hole_2->v_next (hole_3 giallo)
  |                                                  |
  |                                                  |
  hole_3->v_next (hole_4 rosa)         hole_3->v_next (hole_4 rosa)
  |                                                  |
  |                                                  |
  hole_4->v_next (hole_5 bianco)       hole_4->v_next (hole_5 bianco)
  |                                                  |
  |                                                  |
  hole_5->v_next (hole_6 grigio scuro)     hole_5->v_next (hole_6 grigio scuro)
  |                                                  |
  |                                                  |
  hole_6->v_next (hole_7 nero)         hole_6->v_next (hole_7 nero)
  |                                                  |
  |                                                  |
  hole_7->v_next (hole_8 grigio chiaro)     hole_7->v_next (hole_8 grigio chiaro)