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 ? 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;
}