opencv识别正方形（矩形）代码

#include "cv.h"#include "highgui.h"#include <stdio.h>#include <math.h>#include <string.h>#include <iostream>int thresh = 50;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, c, l, N = 11; CvSize sz = cvSize( img->width & -2, img->height & -2 );   IplImage* timg = cvCloneImage( img ); IplImage* gray = cvCreateImage( sz, 8, 1 ); IplImage* pyr = cvCreateImage( cvSize(sz.width/2, sz.height/2), 8, 3 ); IplImage* tgray; 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 ); cvSetImageROI( timg, cvRect( 0, 0, sz.width, sz.height )); // 过滤噪音 cvPyrDown( timg, pyr, 7 ); cvPyrUp( pyr, timg, 7 ); tgray = cvCreateImage( sz, 8, 1 ); // 红绿蓝3色分别尝试提取 for( c = 0; c < 3; c++ ) {  // 提取 the c-th color plane  cvSetImageCOI( timg, c+1 );  cvCopy( timg, tgray, 0 );  // 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( tgray, gray, 0, thresh, 5 );    //使用任意结构元素膨胀图像    cvDilate( gray, gray, 0, 1 );   }   else   {    // apply threshold if l!=0:    cvThreshold( tgray, gray, (l+1)*255/N, 255, CV_THRESH_BINARY );   }   // 找到所有轮廓并且存储在序列中   cvFindContours( gray, 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)) < 100000 &&     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;   }  } } cvReleaseImage( &gray ); cvReleaseImage( &pyr ); cvReleaseImage( &tgray ); cvReleaseImage( &timg ); 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; 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 );  // draw the square as a closed polyline  cvPolyLine( cpy, &rect, &count, 1, 1, CV_RGB(0,255,0), 2, CV_AA, 0 ); } cvShowImage( wndname, cpy ); cvReleaseImage( &cpy );}char* names[] = { "pic1.png", "pic2.png", "pic3.png",     "pic4.png", "pic5.png", "pic6.png","pic7.png","pic8.png",     "pic9.png","pic10.png","pic11.png","pic12.png", 0 };int main(int argc, char** argv){ int i, c; storage = cvCreateMemStorage(0); for( i = 0; names[i] != 0; i++ ) {  img0 = cvLoadImage( names[i], 1 );  if( !img0 )  {   cout<<"不能载入"<<names[i]<<"继续下一张图片"<<endl;   continue;  }  img = cvCloneImage( img0 );  cvNamedWindow( wndname, 1 );  // find and draw the squares  drawSquares( img, findSquares4( img, storage ) );  c = cvWaitKey(0);    cvReleaseImage( &img );  cvReleaseImage( &img0 );  cvClearMemStorage( storage );  if( (char)c == 27 )   break; } cvDestroyWindow( wndname ); return 0;}