//正方形检测源码

//载入数张包含各种形状的图片，检测出其中的正方形

#include "cv.h"

#include "highgui.h"

#include

#include

#include

#include

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<

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;

}