Doxygen tutorials: cpp done
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@@ -23,7 +23,7 @@ Theory
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where \f$(x_{center}, y_{center})\f$ define the center position (green point) and \f$r\f$ is the radius,
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which allows us to completely define a circle, as it can be seen below:
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- For sake of efficiency, OpenCV implements a detection method slightly trickier than the standard
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Hough Transform: *The Hough gradient method*, which is made up of two main stages. The first
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@@ -34,82 +34,35 @@ Theory
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Code
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----
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1. **What does this program do?**
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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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2. The sample code that we will explain can be downloaded from
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|TutorialHoughCirclesSimpleDownload|_. A slightly fancier version (which shows trackbars for
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changing the threshold values) can be found |TutorialHoughCirclesFancyDownload|_.
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@code{.cpp}
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#include "opencv2/highgui.hpp"
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#include "opencv2/imgproc.hpp"
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#include <iostream>
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#include <stdio.h>
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-# The sample code that we will explain can be downloaded from [here](https://github.com/Itseez/opencv/tree/master/samples/cpp/houghcircles.cpp).
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A slightly fancier version (which shows trackbars for
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changing the threshold values) can be found [here](https://github.com/Itseez/opencv/tree/master/samples/cpp/tutorial_code/ImgTrans/HoughCircle_Demo.cpp).
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@includelineno samples/cpp/houghcircles.cpp
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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, COLOR_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, 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", 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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@endcode
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Explanation
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-----------
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1. Load an image
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-# Load an image
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@code{.cpp}
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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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@endcode
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2. Convert it to grayscale:
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-# Convert it to grayscale:
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@code{.cpp}
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cvtColor( src, src_gray, COLOR_BGR2GRAY );
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@endcode
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3. Apply a Gaussian blur to reduce noise and avoid false circle detection:
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-# Apply a Gaussian blur to reduce noise and avoid false circle detection:
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@code{.cpp}
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GaussianBlur( src_gray, src_gray, Size(9, 9), 2, 2 );
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@endcode
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4. Proceed to apply Hough Circle Transform:
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-# Proceed to apply Hough Circle Transform:
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@code{.cpp}
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vector<Vec3f> circles;
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@@ -129,7 +82,7 @@ Explanation
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- *min_radius = 0*: Minimum radio to be detected. If unknown, put zero as default.
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- *max_radius = 0*: Maximum radius to be detected. If unknown, put zero as default.
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5. Draw the detected circles:
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-# Draw the detected circles:
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@code{.cpp}
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for( size_t i = 0; i < circles.size(); i++ )
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{
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@@ -143,19 +96,19 @@ Explanation
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@endcode
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You can see that we will draw the circle(s) on red and the center(s) with a small green dot
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6. Display the detected circle(s):
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-# Display the detected circle(s):
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@code{.cpp}
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namedWindow( "Hough Circle Transform Demo", WINDOW_AUTOSIZE );
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imshow( "Hough Circle Transform Demo", src );
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@endcode
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7. Wait for the user to exit the program
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-# Wait for the user to exit the program
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@code{.cpp}
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waitKey(0);
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@endcode
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Result
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------
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The result of running the code above with a test image is shown below:
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