OPENCV检测矩形并计算其中心

#include "cv.h"  
#include "highgui.h"  
#include  
#include  
#include  
  
#pragma comment(lib, "cv.lib")  
#pragma comment(lib, "cxcore.lib")  
#pragma comment(lib, "highgui.lib")  
  


    
IplImage* img =NULL;  
IplImage* img0 = NULL;  
CvMemStorage* storage =NULL;  
const char * wndname = "正方形检测 demo";  
  
//angle函数用来返回（两个向量之间找到角度的余弦值）  
double angle( CvPoint* pt1, CvPoint* pt2, CvPoint* pt0 )  
{  
 double dx1 = pt1->x - pt0->x;  
 double dy1 = pt1->y - pt0->y;  
 double dx2 = pt2->x - pt0->x;  
 double dy2 = pt2->y - pt0->y;  
 return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);  
}  
  
// 返回图像中找到的所有轮廓序列，并且序列存储在内存存储器中  
  
CvSeq* findSquares4( IplImage* img, CvMemStorage* storage )  
{  
 CvSeq* contours;  
 int i, l, N = 11;  
  
   
 //IplImage* timg = cvCloneImage( img );  
 //IplImage* gray = cvCreateImage( sz, 8, 1 );  
 //IplImage* pyr = cvCreateImage( cvSize(sz.width/2, sz.height/2), 8, 1 );  


 CvSeq* result;  
 double s, t;  
 // 创建一个空序列用于存储轮廓角点  
 CvSeq* squares = cvCreateSeq( 0, sizeof(CvSeq), sizeof(CvPoint), storage );  
  

  // 尝试各种阈值提取得到的（N=11）  
  for( l = 0; l < N; l++ )  
  {  
   // apply Canny. Take the upper threshold from slider  
   // Canny helps to catch squares with gradient shading    
   if( l == 0 )  
   {  
  
cvCanny( img, img, 100,255, 3 );  //正常情况下
    //使用任意结构元素膨胀图像  
    cvDilate( img, img, 0, 1 );  
   }  
   else  
   {  
    // apply threshold if l!=0:  
    cvThreshold( img, img, (l+1)*255/N, 255, CV_THRESH_BINARY );  
   }  
  
   // 找到所有轮廓并且存储在序列中  
   cvFindContours( img, storage, &contours, sizeof(CvContour),  
    CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0) );  
  
   // 遍历找到的每个轮廓contours  
   while( contours )  
   {  
     //用指定精度逼近多边形曲线  
    result = cvApproxPoly( contours, sizeof(CvContour), storage,  
     CV_POLY_APPROX_DP, cvContourPerimeter(contours)*0.02, 0 );  
                    
  
    if( result->total == 4 &&  
     fabs(cvContourArea(result,CV_WHOLE_SEQ)) > 500 &&  
     fabs(cvContourArea(result,CV_WHOLE_SEQ)) < 1000000 &&  
     cvCheckContourConvexity(result) )  
    {  
     s = 0;  
  
     for( i = 0; i < 5; i++ )  
     {  
      // find minimum angle between joint edges (maximum of cosine)  
      if( i >= 2 )  
      {  
       t = fabs(angle(  
        (CvPoint*)cvGetSeqElem( result, i ),  
        (CvPoint*)cvGetSeqElem( result, i-2 ),  
        (CvPoint*)cvGetSeqElem( result, i-1 )));  
       s = s > t ? s : t;  
      }  
     }  
  
     // if 余弦值 足够小，可以认定角度为90度直角  
     //cos0.1=83度，能较好的趋近直角  
     if( s < 0.1 )    
      for( i = 0; i < 4; i++ )  
       cvSeqPush( squares,  
       (CvPoint*)cvGetSeqElem( result, i ));  
    }  
  
    // 继续查找下一个轮廓  
    contours = contours->h_next;  
   }  
  }  
  
  
 return squares;  
}  
  
//drawSquares函数用来画出在图像中找到的所有正方形轮廓  
void drawSquares( IplImage* img, CvSeq* squares )  
{  
 CvSeqReader reader; 
 CvPoint pt3;
 IplImage* cpy = cvCloneImage( img );  
 int i;  
 cvStartReadSeq( squares, &reader, 0 );  
  
 // read 4 sequence elements at a time (all vertices of a square)  
 for( i = 0; i < squares->total; i += 4 )  
 {  
  CvPoint pt[4], *rect = pt;  
  int count = 4;  
  
  // read 4 vertices  
  CV_READ_SEQ_ELEM( pt[0], reader );  
  CV_READ_SEQ_ELEM( pt[1], reader );  
  CV_READ_SEQ_ELEM( pt[2], reader );  
  CV_READ_SEQ_ELEM( pt[3], reader );
  pt3.x=(pt[0].x+pt[1].x+pt[2].x+pt[3].x)/4;
  pt3.y=(pt[0].y+pt[1].y+pt[2].y+pt[3].y)/4;
  cvLine(cpy,pt3,pt3,CV_RGB(255, 255, 255),4,8,0);
  printf("(%d,%d)",pt3.x,pt3.y);
  
  // draw the square as a closed polyline  
  cvPolyLine( cpy, &rect, &count, 1, 1, CV_RGB(255,255,255), 2, CV_AA, 0 );  
 }  
  
 cvShowImage( wndname, cpy );  
 cvReleaseImage( &cpy );  
}  
  
    
  
int main(int argc, char** argv)  
{  
  
 storage = cvCreateMemStorage(0);  
  
  
  img0 = cvLoadImage( "000.jpg", 0 );  
  
  img = cvCloneImage( img0 );  
  cvNamedWindow( wndname, 1 );  
  
  // find and draw the squares  
  drawSquares( img, findSquares4( img, storage ) );  
  
  cvWaitKey(0);  
    
  cvReleaseImage( &img );  
  cvReleaseImage( &img0 );  
  
  cvClearMemStorage( storage );  
  
 cvDestroyWindow( wndname );  


}