.. _find_contours: Finding contours in your image ****************************** Goal ===== In this tutorial you will learn how to: .. container:: enumeratevisibleitemswithsquare * Use the OpenCV function :find_contours:`findContours <>` * Use the OpenCV function :draw_contours:`drawContours <>` 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( " Canny thresh:", "Source", &thresh, max_thresh, thresh_callback ); thresh_callback( 0, 0 ); waitKey(0); return(0); } /** @function thresh_callback */ void thresh_callback(int, void* ) { Mat canny_output; vector > contours; vector hierarchy; /// Detect edges using canny Canny( src_gray, canny_output, thresh, thresh*2, 3 ); /// Find contours findContours( canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) ); /// Draw contours Mat drawing = Mat::zeros( canny_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, 2, 8, hierarchy, 0, Point() ); } /// Show in a window namedWindow( "Contours", CV_WINDOW_AUTOSIZE ); imshow( "Contours", drawing ); } Explanation ============ Result ====== #. Here it is: ============= ============= |contour_0| |contour_1| ============= ============= .. |contour_0| image:: images/Find_Contours_Original_Image.jpg :align: middle .. |contour_1| image:: images/Find_Contours_Result.jpg :align: middle