opencv如何实现矩形检测

#include "cv.h"
#include "highgui.h"
#include <stdio.h>
#include <math.h>
#include <string.h>


//////////////////////////////////////////////////////////////////
//函数功能：用向量来做COSα=两向量之积/两向量模的乘积求两条线段夹角
//输入：  线段3个点坐标pt1,pt2,pt0,最后一个参数为公共点
//输出：  线段夹角，单位为角度
//////////////////////////////////////////////////////////////////
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;  
  double angle_line = (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);//余弦值
  return acos(angle_line)*180/3.141592653; 
}
//////////////////////////////////////////////////////////////////
//函数功能：采用多边形检测，通过约束条件寻找矩形
//输入：  img 原图像
//     storage 存储
//     minarea，maxarea 检测矩形的最小/最大面积
//     minangle,maxangle 检测矩形边夹角范围，单位为角度
//输出：  矩形序列
//////////////////////////////////////////////////////////////////
CvSeq* findSquares4( IplImage* img, CvMemStorage* storage ,int minarea, int maxarea, int minangle, int maxangle)
{ 
  CvSeq* contours;//边缘
  int N = 6; //阈值分级
  CvSize sz = cvSize( img->width & -2, img->height & -2 );
  IplImage* timg = cvCloneImage( img );//拷贝一次img
  IplImage* gray = cvCreateImage( sz, 8, 1 ); //img灰度图
  IplImage* pyr = cvCreateImage( cvSize(sz.width/2, sz.height/2), 8, 3 ); //金字塔滤波3通道图像中间变量
  IplImage* tgray = cvCreateImage( sz, 8, 1 ); ;  
  CvSeq* result; 
  double s, t; 
  CvSeq* squares = cvCreateSeq( 0, sizeof(CvSeq), sizeof(CvPoint), storage );  

  cvSetImageROI( timg, cvRect( 0, 0, sz.width, sz.height ));  
  //金字塔滤波 
  cvPyrDown( timg, pyr, 7 ); 
  cvPyrUp( pyr, timg, 7 );  
  //在3个通道中寻找矩形 
  for( int c = 0; c < 3; c++ ) //对3个通道分别进行处理 
  {    
    cvSetImageCOI( timg, c+1 );   
    cvCopy( timg, tgray, 0 ); //依次将BGR通道送入tgray     
    for( int l = 0; l < N; l++ )   
    {     
      //不同阈值下二值化
      cvThreshold( tgray, gray, (l+1)*255/N, 255, CV_THRESH_BINARY );

      cvFindContours( gray, storage, &contours, sizeof(CvContour),CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0) );     
      while( contours )  
      { //多边形逼近       
       result = cvApproxPoly( contours, sizeof(CvContour), storage,CV_POLY_APPROX_DP, cvContourPerimeter(contours)*0.02, 0 ); 
        //如果是凸四边形并且面积在范围内
       if( result->total == 4 && fabs(cvContourArea(result,CV_WHOLE_SEQ)) > minarea && fabs(cvContourArea(result,CV_WHOLE_SEQ)) < maxarea && cvCheckContourConvexity(result) ) 
        {        
          s = 0;   
          //判断每一条边
          for( int i = 0; i < 5; i++ ) 
          {          
            if( i >= 2 )      
            {  //角度      
              t = fabs(angle( (CvPoint*)cvGetSeqElem( result, i ),(CvPoint*)cvGetSeqElem( result, i-2 ),(CvPoint*)cvGetSeqElem( result, i-1 )));  
              s = s > t &#63; s : t;   
            }     
          }  
          //这里的S为直角判定条件 单位为角度
          if( s > minangle && s < maxangle )           
            for( int i = 0; i < 4; i++ )       
              cvSeqPush( squares,(CvPoint*)cvGetSeqElem( result, i ));   
        }                   
        contours = contours->h_next;   
      }  
    } 
  }
  cvReleaseImage( &gray );  
  cvReleaseImage( &pyr ); 
  cvReleaseImage( &tgray ); 
  cvReleaseImage( &timg );  
  return squares;
} 
//////////////////////////////////////////////////////////////////
//函数功能：画出所有矩形
//输入：  img 原图像
//     squares 矩形序列
//     wndname 窗口名称
//输出：  图像中标记矩形
//////////////////////////////////////////////////////////////////
void drawSquares( IplImage* img, CvSeq* squares ,const char* wndname)
{  
  CvSeqReader reader;  
  IplImage* cpy = cvCloneImage( img );  
  CvPoint pt[4];
  int i;    
  cvStartReadSeq( squares, &reader, 0 );   
  for( i = 0; i < squares->total; i += 4 ) 
  {    
    CvPoint* rect = pt;  
    int count = 4;   
    memcpy( pt, reader.ptr, squares->elem_size ); 
    CV_NEXT_SEQ_ELEM( squares->elem_size, reader ); 
    memcpy( pt + 1, reader.ptr, squares->elem_size );   
    CV_NEXT_SEQ_ELEM( squares->elem_size, reader );  
    memcpy( pt + 2, reader.ptr, squares->elem_size );  
    CV_NEXT_SEQ_ELEM( squares->elem_size, reader );   
    memcpy( pt + 3, reader.ptr, squares->elem_size ); 
    CV_NEXT_SEQ_ELEM( squares->elem_size, reader );     
    //cvPolyLine( cpy, &rect, &count, 1, 1, CV_RGB(0,255,0), 3, CV_AA, 0 );
    cvPolyLine( cpy, &rect, &count, 1, 1, CV_RGB(rand()&255,rand()&255,rand()&255), 1, CV_AA, 0 );//彩色绘制
  }    
  cvShowImage( wndname, cpy ); 
  cvReleaseImage( &cpy );
}

int main()
{  
  CvCapture* capture = cvCreateCameraCapture(0);
  IplImage* img0 = 0;
  CvMemStorage* storage = 0;
  int c; 
  const char* wndname = "Square Detection Demo"; //窗口名称
  storage = cvCreateMemStorage(0);  
  cvNamedWindow( wndname, 1 );  
  while (true)
  {
    img0 = cvQueryFrame(capture);   
    drawSquares( img0, findSquares4( img0, storage, 100, 2000, 80, 100), wndname );
    cvClearMemStorage( storage ); //清空存储
    c = cvWaitKey(10); 
    if( c == 27 )    
    break; 
  }

  cvReleaseImage( &img0 );    
  cvClearMemStorage( storage ); 

  cvDestroyWindow( wndname );  
  return 0;
}