116 lines
2.9 KiB
ReStructuredText
116 lines
2.9 KiB
ReStructuredText
.. _hull:
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Convex Hull
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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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.. container:: enumeratevisibleitemswithsquare
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* Use the OpenCV function :convex_hull:`convexHull <>`
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Theory
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======
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Code
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====
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This tutorial code's is shown lines below. You can also download it from `here <https://github.com/Itseez/opencv/tree/master/samples/cpp/tutorial_code/ShapeDescriptors/hull_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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#include <stdlib.h>
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using namespace cv;
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using namespace std;
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Mat src; Mat src_gray;
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int thresh = 100;
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int max_thresh = 255;
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RNG rng(12345);
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/// Function header
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void thresh_callback(int, void* );
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/** @function main */
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int main( int argc, char** argv )
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{
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/// Load source image and convert it to gray
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src = imread( argv[1], 1 );
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/// Convert image to gray and blur it
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cvtColor( src, src_gray, CV_BGR2GRAY );
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blur( src_gray, src_gray, Size(3,3) );
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/// Create Window
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char* source_window = "Source";
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namedWindow( source_window, CV_WINDOW_AUTOSIZE );
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imshow( source_window, src );
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createTrackbar( " Threshold:", "Source", &thresh, max_thresh, thresh_callback );
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thresh_callback( 0, 0 );
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waitKey(0);
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return(0);
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}
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/** @function thresh_callback */
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void thresh_callback(int, void* )
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{
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Mat src_copy = src.clone();
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Mat threshold_output;
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vector<vector<Point> > contours;
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vector<Vec4i> hierarchy;
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/// Detect edges using Threshold
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threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY );
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/// Find contours
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findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );
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/// Find the convex hull object for each contour
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vector<vector<Point> >hull( contours.size() );
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for( int i = 0; i < contours.size(); i++ )
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{ convexHull( Mat(contours[i]), hull[i], false ); }
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/// Draw contours + hull results
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Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
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for( int i = 0; i< contours.size(); i++ )
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{
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Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
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drawContours( drawing, contours, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
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drawContours( drawing, hull, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
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}
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/// Show in a window
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namedWindow( "Hull demo", CV_WINDOW_AUTOSIZE );
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imshow( "Hull demo", drawing );
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}
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Explanation
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============
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Result
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======
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#. Here it is:
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========== ==========
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|Hull_0| |Hull_1|
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========== ==========
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.. |Hull_0| image:: images/Hull_Original_Image.jpg
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:align: middle
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.. |Hull_1| image:: images/Hull_Result.jpg
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:align: middle
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