[OpenCV] cvConvexHull2

test_ocv.zip

cvConvexHull2() 함수의 사용

CvSeq* cvConvexHull2( const CvArr* input, void* hull_storage=NULL,
                      int orientation=CV_CLOCKWISE, int return_points=0 );

points

Sequence or array of 2D points with 32-bit integer or floating-point coordinates.

hull_storage

The destination array (CvMat*) or memory storage (CvMemStorage*) that will store the convex hull. If it is array, it should be 1d and have the same number of elements as the input array/sequence. On output the header is modified: the number of columns/rows is truncated down to the hull size.

orientation

Desired orientation of convex hull: CV_CLOCKWISE or CV_COUNTER_CLOCKWISE.

return_points

If non-zero, the points themselves will be stored in the hull instead of indices if hull_storage is array, or pointers if hull_storage is memory storage.

The function cvConvexHull2 finds convex hull of 2D point set using Sklansky’s algorithm. If hull_storage is memory storage, the function creates a sequence containing the hull points or pointers to them, depending on return_points value and returns the sequence on output.

결과

소스코드

#include "cv.h"
#include "highgui.h"
#include <stdlib.h>
#define ARRAY  0 /* switch between array/sequence method by replacing 0<=>1 */
void main( int argc, char** argv )
{
 IplImage* img = cvCreateImage( cvSize( 500, 500 ), 8, 3 );
 cvNamedWindow( "hull", 1 );
 CvMemStorage* storage = cvCreateMemStorage();

 for(;;)
 {
  // ---------------------------------------------------------------------
  // randoms, Init
  // ---------------------------------------------------------------------
  int i, count = rand()%100 + 1, hullcount;
  CvPoint pt0;
  CvSeq* ptseq = cvCreateSeq( CV_SEQ_KIND_GENERIC|CV_32SC2, sizeof(CvContour),
   sizeof(CvPoint), storage );
  CvSeq* hull;
  
  for( i = 0; i < count; i++ )
  {
   pt0.x = rand() % (img->width/2) + img->width/4;
   pt0.y = rand() % (img->height/2) + img->height/4;
   cvSeqPush( ptseq, &pt0 );
  }
  // ---------------------------------------------------------------------
  // ---------------------------------------------------------------------
  // Compute ConvexHull
  // ---------------------------------------------------------------------
  hull = cvConvexHull2( ptseq, 0, CV_CLOCKWISE, 0 );
  // ---------------------------------------------------------------------

  // ---------------------------------------------------------------------
  // Draw Point
  // ---------------------------------------------------------------------
  hullcount = hull->total;
  cvZero( img );
  for( i = 0; i < count; i++ )
  {
   pt0 = *CV_GET_SEQ_ELEM( CvPoint, ptseq, i );
   cvCircle( img, pt0, 2, CV_RGB( 255, 0, 0 ), CV_FILLED );
  }
  // ---------------------------------------------------------------------
  // ---------------------------------------------------------------------
  // Draw Line
  // ---------------------------------------------------------------------
  pt0 = **CV_GET_SEQ_ELEM( CvPoint*, hull, hullcount - 1 );
  for( i = 0; i < hullcount; i++ )
  {
   CvPoint pt = **CV_GET_SEQ_ELEM( CvPoint*, hull, i );
   cvLine( img, pt0, pt, CV_RGB( 0, 255, 0 ));
   pt0 = pt;
  }
  // ---------------------------------------------------------------------
  cvShowImage( "hull", img );
  int key = cvWaitKey(0);
  if( key == 27 ) // 'ESC'
   break;
  cvClearMemStorage( storage );
 }
}

참조 URL
[1] http://blog.naver.com/winamq?Redirect=Log&logNo=70081753321