How can i get accurate center points? - c++

Question

How can I get accurate center points with OpenCV Hough Circle Transformation? I need more decimal places of accurate in the x,y coordinates.
( on accurate i mean something like this)
i got these center coordinates with matlab
x107,775526315904 y112,963480232638
x469,550463441518 y208,309866770404
x217,386414755458 y490,882895036058
Here is my code:
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/core/core.hpp>
#include <iostream>
#include <stdio.h>
using namespace cv;
using namespace std;
int main()
{
Mat src, src_gray, src0;
printf("Give the name of the picture\n");
char ImageName[20];
scanf("%s", &ImageName);
/// Read the image
src = imread(ImageName, 1);
if (!src.data)
{
printf("no image data\n");
return main();
}
// src0 = src;
// imshow("orignal", src0);
/// Convert it to gray
cvtColor(src, src_gray, CV_BGR2GRAY);
GaussianBlur(src_gray, src_gray, Size(9, 9), 2, 2);
vector<Vec3f> circles;
/// Apply the Hough Transform to find the circles
HoughCircles(src_gray, circles, CV_HOUGH_GRADIENT, 0.92, src_gray.rows / 10, 20, 10, 55, 60);
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]);
// printf("%d center x %d y %d\n", i, cvRound(circles[i][0]), cvRound(circles[i][1]));
// printf("rad: %d\n", cvRound(circles[i][2]));
cout << i + 1 << " centerpoint " << " x: " << circles[i][0] << " y: " << circles[i][1] << "rad: " << circles[i][2] << endl;
// cout << i + 1 << " othermethod" << "x : " << center.x << endl;
// circle center
circle(src, center, 1, Scalar(0, 255, 0), -1, 8, 0);
// circle outline
circle(src, center, radius, Scalar(255, 0, 0), 1, 8, 0);
}
imshow("circlefinder", src);
waitKey(1);
system("PAUSE");
cvDestroyWindow("orignal");
cvDestroyWindow("circlefinder");
printf("new picture ?(y/n)");
char ans[1];
scanf("%s", &ans);
if (strcmp(ans, "y"))
{
return 0;
}
else if (strcmp(ans, "n"))
{
return main();
}
}
Here is the output:
Give the name of the picture
as2.jpg
145.5test x
1 centerpoint x: 105.5 y: 112.5rad: 55.5563
2 centerpoint x: 235.5 y: 427.5rad: 56.626
3 centerpoint x: 466.5 y: 196.5rad: 55.5203
A folytatáshoz nyomjon meg egy billentyűt . . .
new picture ?

Answer 1

It's not your data what is lost. It's just print function you made skipping some numbers.
Try std::setprecision:
std::cout << 432.123456789f << " " << std::setprecision(10) << 432.123456789f << std::endl;
Don't forget:
#include <iomanip>
Anyway I don't think you really need that precission. Your measure error in image processing is usually quite big and last digits don't give you any real information.