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OpenCV C++ Program for coin detection
  • Difficulty Level : Medium
  • Last Updated : 09 Feb, 2018

The following is the explanation to the C++ code for coin detection in C++ using the tool OpenCV.

Things to know:

  1. The code will only compile in Linux environment.
  2. To run in windows, please use the file: ‘coin.o’ and run it in cmd. However if it does not run(problem in system architecture) then compile it in windows by making suitable and obvious changes to the code like: Use in place of .
  3. Compile command: g++ -w coin.cpp -o coin.exe `pkg-config –libs opencv`
  4. Run command: ./coin
  5. The image containing coin/coins has to be in the same directory as the code.
    Before you run the code, please make sure that you have OpenCV installed on your // system.

Code Snippets Explained:

#include "opencv2/highgui/highgui.hpp"
// highgui - an interface to video and image capturing.

#include "opencv2/imgproc/imgproc.hpp"
// imgproc - An image processing module that for linear and non-linear
 image filtering, geometrical image transformations, color space conversion and so on.
#include <iostream>
#include <stdio.h>
// The header files for performing input and output.
using namespace cv;
// Namespace where all the C++ OpenCV functionality resides.

using namespace std;
// For input output operations.
int main()
    Mat image;
    // Mat object is a basic image container. image is an object of Mat.

    // Take any image but make sure its in the same folder.
    // first argument denotes the image to be loaded. 
    // second argument specifies the image format as follows: 
    // CV_LOAD_IMAGE_UNCHANGED (<0) loads the image as it is.      
    // CV_LOAD_IMAGE_GRAYSCALE ( 0) loads the image in Gray scale.      
    // CV_LOAD_IMAGE_COLOR (>0) loads the image in the BGR format. 
    // If the second argument is not there, it is implied CV_LOAD_IMAGE_COLOR.

    vector coin;
    // A vector data type to store the details of coins.

    HoughCircles(image,coin,CV_HOUGH_GRADIENT,2,20,450,60,0,0 );
    // Argument 1: Input image mode
    // Argument 2: A vector that stores 3 values: x,y and r for each circle.
    // Argument 3: CV_HOUGH_GRADIENT: Detection method.
    // Argument 4: The inverse ratio of resolution.
    // Argument 5: Minimum distance between centers.
    // Argument 6: Upper threshold for Canny edge detector.
    // Argument 7: Threshold for center detection.
    // Argument 8: Minimum radius to be detected. Put zero as default
    // Argument 9: Maximum radius to be detected. Put zero as default

    int l=coin.size();
    // Get the number of coins.

    cout<<"\n The number of coins is: "<<l<<"\n\n";
    // To draw the detected circles.
    for( size_t i = 0; i < coin.size(); i++ )
    Point center(cvRound(coin[i][0]),cvRound(coin[i][1]));
    // Detect center
    // cvRound: Rounds floating point number to nearest integer.
    int radius=cvRound(coin[i][2]);
    // To get the radius from the second argument of vector coin.     
        // circle center
        //  To get the circle outline.     
        // circle outline
    cout<< " Center location for circle "<<i+1<<" :
        "<<center<<"\n Diameter : "<<2*radius<<"\n";
    namedWindow("Coin Counter",CV_WINDOW_AUTOSIZE);
    // Create a window called 
    // first argument: name of the window. 
    // second argument: flag- types: 
    // WINDOW_NORMAL : The user can resize the window. 
    // WINDOW_AUTOSIZE : The window size is automatically adjusted to fit the
     // displayed image() ), and you cannot change the window size manually. 
    // WINDOW_OPENGL : The window will be created with OpenGL support.
    imshow("Coin Counter",image);
    // first argument: name of the window 
    // second argument: image to be shown(Mat object)

    waitKey(0); // Wait for infinite time for a key press.

    Return 0;    // Return from main function.

End of explanation.

About the Author:

Aditya Prakash is an undergraduate student at Indian Institute of Information Technology, Vadodara. He primarily codes in C++. The motto for him is: So far so good. He plays cricket, watches superhero movies, football and is a big fan of answering questions.

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