79 lines
2.2 KiB
ReStructuredText
79 lines
2.2 KiB
ReStructuredText
.. _hough_circle:
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Hough Circle Transform
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***********************
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Goal
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=====
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In this tutorial you will learn how to:
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* Use the OpenCV functions :hough_circles:`HoughCircles <>` to detect circles in an image.
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Code
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======
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#. **What does this program do?**
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* Loads an image and blur it to reduce the noise
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* Applies the *Hough Circle Transform* to the blurred image .
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* Display the detected circle in a window.
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#. The sample code that we will explain can be downloaded from `here <https://code.ros.org/svn/opencv/trunk/opencv/samples/cpp/houghlines.cpp>`_. A slightly fancier version (which shows both Hough standard and probabilistic with trackbars for changing the threshold values) can be found `here <https://code.ros.org/svn/opencv/trunk/opencv/samples/cpp/tutorial_code/ImgTrans/HoughCircle_Demo.cpp>`_
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.. code-block:: cpp
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#include "opencv2/highgui/highgui.hpp"
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#include "opencv2/imgproc/imgproc.hpp"
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#include <iostream>
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#include <stdio.h>
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using namespace cv;
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/** @function main */
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int main(int argc, char** argv)
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{
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Mat src, src_gray;
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/// Read the image
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src = imread( argv[1], 1 );
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if( !src.data )
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{ return -1; }
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/// Convert it to gray
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cvtColor( src, src_gray, CV_BGR2GRAY );
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/// Reduce the noise so we avoid false circle detection
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GaussianBlur( src_gray, src_gray, Size(9, 9), 2, 2 );
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vector<Vec3f> circles;
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/// Apply the Hough Transform to find the circles
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HoughCircles( src_gray, circles, CV_HOUGH_GRADIENT, 1, src_gray.rows/8, 200, 100, 0, 0 );
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/// Draw the circles detected
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for( size_t i = 0; i < circles.size(); i++ )
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{
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Point center(cvRound(circles[i][0]), cvRound(circles[i][1]));
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int radius = cvRound(circles[i][2]);
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// circle center
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circle( src, center, 3, Scalar(0,255,0), -1, 8, 0 );
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// circle outline
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circle( src, center, radius, Scalar(0,0,255), 3, 8, 0 );
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}
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/// Show your results
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namedWindow( "Hough Circle Transform Demo", CV_WINDOW_AUTOSIZE );
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imshow( "Hough Circle Transform Demo", src );
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waitKey(0);
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return 0;
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}
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Result
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=======
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.. image:: images/Hough_Circle_Tutorial_Result.jpg
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:alt: Result of detecting circles with Hough Transform
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:align: center
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