图像上找线、圆

/* Finds lines on binary image using one of several methods.
   line_storage is either memory storage or 1 x <max number of lines> CvMat, its
   number of columns is changed by the function.
   method is one of CV_HOUGH_*;
   rho, theta and threshold are used for each of those methods;
   param1 ~ line length, param2 ~ line gap - for probabilistic,

   param1 ~ srn, param2 ~ stn - for multi-scale */

CVAPI(CvSeq*)  cvHoughLines2( CvArr* image, void* line_storage, int method,
                              double rho, double theta, int threshold,
                              double param1 CV_DEFAULT(0), double param2 CV_DEFAULT(0));

找线实例：

CvMemStorage* _pStorage = cvCreateMemStorage(0);
CvSeq* _lines=cvHoughLines2(_grayImg,_pStorage,CV_HOUGH_PROBABILISTIC,1,CV_PI/180,50,5,10);

/* Finds circles in the image */
CVAPI(CvSeq*) cvHoughCircles( CvArr* image, void* circle_storage,
                              int method, double dp, double min_dist,
                              double param1 CV_DEFAULT(100),
                              double param2 CV_DEFAULT(100),
                              int min_radius CV_DEFAULT(0),

                              int max_radius CV_DEFAULT(0));

切记：在循环使用中，每次检测完后要cvClearMemStorage(storage);否则的话一直检测，则存储的线或圆的内存会一直保存在storage中，就会出现内存泄露。

cvHoughLines2和cvHoughCircles使用范例。有图，有程序。

cvHoughLines2需要的是Binary image。 cvHoughCircles 需要的是灰度图，而且它会自动调用cvSobel函数。

关于cvHoughCircles多说一句，之前最好用cvSmooth一下，否则会有很多错误的圆被识别出来。

cvHoughLines2

orginal

lines.jpg (99.05 KiB) 被浏览 4777 次

cvHoughCircles 

cccc1.jpg (12.69 KiB) 被浏览 4777 次

（VS2008+open1.1,注意图片路径）

 <span style="background-color: rgb(255, 255, 255);">#include "stdafx.h"
 #include <iostream>

 #include <cv.h>
 #include <cxcore.h>
 #include <highgui.h>
 #include <math.h>
 using namespace std;
 /*
 coded and updated by Huang, Haiqiao 2010-01-13
 Examples of using cvHoughLines2 and cvHoughCircles
 */

 int main(int argc, char** argv)
 {
    int i;
    cout << "Lines and Circles OpenCV!"<<endl;  //\\cameraman.jpg
    char* filename="D:\\OpenCV_stuff\\SampleImages\\pattern512.bmp";
    IplImage* imgRGB = cvLoadImage(filename);
    IplImage* imgGrey = cvLoadImage(filename,0); //grey image
    char* filename1="D:\\OpenCV_stuff\\SampleImages\\circle3.jpg";
    IplImage* imgcircle = cvLoadImage(filename1,1); //color image
    if (imgGrey==NULL){
       cout << "No valid image input."<<endl;
       char c=getchar();
       return 1;
    }

    IplImage* cannyImg  = cvCreateImage(cvSize(imgGrey->width,imgGrey->height),IPL_DEPTH_8U,1);
    cvCanny(imgGrey,cannyImg,170,200,3);

    //************hough lines**probabilistic********//
    CvMemStorage* storage = cvCreateMemStorage(0);
         CvSeq* lines = 0;
    double rho=1;
    double theta=CV_PI/180;
    double threshold=30;
    double min_length=40;//CV_HOUGH_PROBABILISTIC
    double sepration_connection=20;//CV_HOUGH_PROBABILISTIC

    //binary image is needed.
 cvClearMemStorage(storage);
     lines = cvHoughLines2(
       cannyImg,
       storage,
       CV_HOUGH_PROBABILISTIC,
       rho,
       theta,
       threshold,
       min_length,
       sepration_connection);

    //draw lines found by cvHoughLines2
     for( i = 0; i < lines->total; i++ )
     {
        CvPoint* line = (CvPoint*)cvGetSeqElem(lines,i);
        cvLine(imgRGB, line[0], line[1], CV_RGB(255,0,0),1, 8 );//cannyImgColor
     }



    /*
       Circle identification
    */
    IplImage* grayimgcircle = cvCreateImage( cvGetSize(imgcircle), 8, 1 );
    CvMemStorage* storagecircle = cvCreateMemStorage(0);
     cvCvtColor( imgcircle, grayimgcircle, CV_BGR2GRAY );
    // smooth it, otherwise a lot of false circles may be detected
     cvSmooth( grayimgcircle, grayimgcircle, CV_GAUSSIAN, 9, 9 );

    double dp=2;
    double min_dist=10;
    int min_radius=5;
    int max_radius=150;
    //only greyimage is needed. cvHoughCircles would call cvSobel() internally.
 cvClearMemStorage(storage);
    CvSeq* circles = cvHoughCircles(
          grayimgcircle,
          storagecircle,
          CV_HOUGH_GRADIENT,
          dp,
          min_dist,
          min_radius,
          max_radius );

     //draw found curves
     for( i = 0; i < circles->total; i++ )
     {
          float* p = (float*)cvGetSeqElem( circles, i );
          cvCircle( imgcircle, cvPoint(cvRound(p[0]),cvRound(p[1])), cvRound(p[2]), CV_RGB(255,0,0), 3, 8, 0 );
     }



     cvNamedWindow( "Circles", CV_WINDOW_AUTOSIZE );
     cvShowImage( "Circles", imgcircle );
    cvNamedWindow("Original", CV_WINDOW_AUTOSIZE );
    cvShowImage( "Original", imgRGB );

    cvWaitKey(0);

    cvDestroyWindow("HoughLines");
    cvReleaseImage(&imgGrey);
    cvDestroyWindow("Original");
    cvReleaseImage(&imgcircle);
    cvDestroyWindow("Circles");

    //char c=getchar();
    return 0;
 }</span>