.. _hull: Convex Hull *********** Goal ===== In this tutorial you will learn how to: .. container:: enumeratevisibleitemswithsquare * Use the OpenCV function :convex_hull:`convexHull <>` Theory ====== Code ==== This tutorial code's is shown lines below. You can also download it from `here `_ .. code-block:: cpp #include "opencv2/highgui/highgui.hpp" #include "opencv2/imgproc/imgproc.hpp" #include #include #include using namespace cv; using namespace std; Mat src; Mat src_gray; int thresh = 100; int max_thresh = 255; RNG rng(12345); /// Function header void thresh_callback(int, void* ); /** @function main */ int main( int argc, char** argv ) { /// Load source image and convert it to gray src = imread( argv[1], 1 ); /// Convert image to gray and blur it cvtColor( src, src_gray, CV_BGR2GRAY ); blur( src_gray, src_gray, Size(3,3) ); /// Create Window char* source_window = "Source"; namedWindow( source_window, CV_WINDOW_AUTOSIZE ); imshow( source_window, src ); createTrackbar( " Threshold:", "Source", &thresh, max_thresh, thresh_callback ); thresh_callback( 0, 0 ); waitKey(0); return(0); } /** @function thresh_callback */ void thresh_callback(int, void* ) { Mat src_copy = src.clone(); Mat threshold_output; vector > contours; vector hierarchy; /// Detect edges using Threshold threshold( src_gray, threshold_output, thresh, 255, THRESH_BINARY ); /// Find contours findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) ); /// Find the convex hull object for each contour vector >hull( contours.size() ); for( int i = 0; i < contours.size(); i++ ) { convexHull( Mat(contours[i]), hull[i], false ); } /// Draw contours + hull results Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 ); for( int i = 0; i< contours.size(); i++ ) { Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) ); drawContours( drawing, contours, i, color, 1, 8, vector(), 0, Point() ); drawContours( drawing, hull, i, color, 1, 8, vector(), 0, Point() ); } /// Show in a window namedWindow( "Hull demo", CV_WINDOW_AUTOSIZE ); imshow( "Hull demo", drawing ); } Explanation ============ Result ====== #. Here it is: ========== ========== |Hull_0| |Hull_1| ========== ========== .. |Hull_0| image:: images/Hull_Original_Image.jpg :align: middle .. |Hull_1| image:: images/Hull_Result.jpg :align: middle