Detect/Fitting Circles using Hough Transform in OpenCV 2.4.6 - opencv

Question

The objective is to detect the 5 white circles in the image.The test image in which the circles have to be detected is the one shown here 640x480
Please download the original image here,1280x1024
I am using different methods to bring out a evaluation of various circle/ellipse detection methods. But somehow I am not able to fix my simple Hough transform code. It does not detect any circles. I am not clear whether the problem is with pre-processing step, or the parameters of the HoughCircle. I have gone through all the similar questions in the forum, but still not able to fix the issue. This is my code. Please help me in this regards..
Header file
#ifndef IMGPROCESSOR_H
#define IMGPROCESSOR_H
// OpenCV Library
#include <opencv2\opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;
class ImgProcessor{
public:
Mat OpImg ;
ImgProcessor();
~ImgProcessor();
//aquire filter methods to image
int Do_Hough(Mat IpImg);
};
#endif /* ImgProcessor_H */
Source file
#include "ImgProcessor.h"
#include <opencv2\opencv.hpp>
#include "opencv2\imgproc\imgproc.hpp"
#include "opencv2\imgproc\imgproc_c.h"
#include <vector>
using namespace cv;
ImgProcessor::ImgProcessor(){
return;
}
ImgProcessor::~ImgProcessor(){
return;
}
//Apply filtering for the input image
int ImgProcessor::Do_Hough(Mat IpImg)
{
//Parameter Initialization________________________________________________________
double sigma_x, sigma_y, thresh=250, max_thresh = 255;
int ksize_w = 5 ;
int ksize_h = 5;
sigma_x = 0.3*((ksize_w-1)*0.5 - 1) + 0.8 ;
sigma_y = 0.3*((ksize_h-1)*0.5 - 1) + 0.8 ;
vector<Vec3f> circles;
//Read the image as a matrix
Mat TempImg;
//resize(IpImg, IpImg ,Size(), 0.5,0.5, INTER_AREA);
//Preprocessing__________________________________________________________
//Perform initial smoothing
GaussianBlur( IpImg, TempImg, Size(ksize_w, ksize_h),2,2);
//perform thresholding
threshold(TempImg,TempImg, thresh,thresh, 0);
//Remove noise by gaussian smoothing
GaussianBlur( TempImg, TempImg, Size(ksize_w, ksize_h),2,2);
/*imshow("Noisefree Image", TempImg);
waitKey(10000);*/
//Obtain edges
Canny(TempImg, TempImg, 255,240 , 3);
imshow("See Edges", TempImg);
waitKey(10000);
//Increase the line thickness
//dilate(TempImg,TempImg,0,Point(-1,-1),3);
//Hough Circle Method______________________________________________________________
// Apply the Hough Transform to find the circles
HoughCircles( TempImg, circles, 3, 1, TempImg.rows/32, 255, 240, 5, 0 );
// Draw the circles detected
for( size_t i = 0; i < circles.size(); i++ )
{
Point center(cvRound(circles[i][0]), cvRound(circles[i][1]));
int radius = cvRound(circles[i][2]);
// circle center
circle( IpImg, center, 3, Scalar(0,255,0), -1, 8, 0 );
// circle outline
circle( IpImg, center, radius, Scalar(0,0,255), 3, 8, 0 );
}
// Show your results
namedWindow( "Hough Circle Transform", WINDOW_AUTOSIZE );
imshow( "Hough Circle Transform", IpImg );
// waitKey(0);
return 0;
}
int main(int argc, char** argv)
{
ImgProcessor Iclass;
//char* imageName = argv[1];
string imageName = "D:/Projects/test_2707/test_2707/1.bmp";
Mat IpImg = imread( imageName );
cvtColor(IpImg, IpImg,6,CV_8UC1);
Iclass.Do_Hough(IpImg);
/*Iclass.Do_Contours(IpImg);*/
return 0;
}

Answer 1

The code seems fine, other than for:
HoughCircles( TempImg, circles, 3, 1, TempImg.rows/32, 255, 240, 5, 0 );
Does number 3 in the parameter list correspond to CV_HOUGH_GRADIENT ? It is always better to use definitions instead of numbers.
May be you should test it first with an image with bigger circles. Once you are sure that the rest of the code is correct, you can tune the parameters of HoughCircles.