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hackassin
GitHub Repository: hackassin/learnopencv
 Path: blob/master/Contour-Detection-using-OpenCV/cpp/contour_extraction/contour_extraction.cpp
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#include<opencv2/opencv.hpp>

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#include <iostream>

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using namespace std;

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using namespace cv;

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int main() {

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    /*

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    Contour detection and drawing using different extraction modes to complement 

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    the understanding of hierarchies

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    */

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    Mat image2 = imread("../../input/custom_colors.jpg");

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    Mat img_gray2;

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    cvtColor(image2, img_gray2, COLOR_BGR2GRAY);

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    Mat thresh2;

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    threshold(img_gray2, thresh2, 150, 255, THRESH_BINARY);

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    vector<vector<Point>> contours3;

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    vector<Vec4i> hierarchy3;

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    findContours(thresh2, contours3, hierarchy3, RETR_LIST, CHAIN_APPROX_NONE);

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    Mat image_copy4 = image2.clone();

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    drawContours(image_copy4, contours3, -1, Scalar(0, 255, 0), 2);

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    imshow("LIST", image_copy4);

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    waitKey(0);

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    imwrite("contours_retr_list.jpg", image_copy4);

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    destroyAllWindows();

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    vector<vector<Point>> contours4;

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    vector<Vec4i> hierarchy4;

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    findContours(thresh2, contours4, hierarchy4, RETR_EXTERNAL, CHAIN_APPROX_NONE);

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    Mat image_copy5 = image2.clone();

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    drawContours(image_copy5, contours4, -1, Scalar(0, 255, 0), 2);

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    imshow("EXTERNAL", image_copy5);

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    waitKey(0);

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    imwrite("contours_retr_external.jpg", image_copy4);

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    destroyAllWindows();

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    vector<vector<Point>> contours5;

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    vector<Vec4i> hierarchy5;

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    findContours(thresh2, contours5, hierarchy5, RETR_CCOMP, CHAIN_APPROX_NONE);

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    Mat image_copy6 = image2.clone();

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    drawContours(image_copy6, contours5, -1, Scalar(0, 255, 0), 2);

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    imshow("EXTERNAL", image_copy6);

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    waitKey(0);

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    imwrite("contours_retr_ccomp.jpg", image_copy6);

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    destroyAllWindows();

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    vector<vector<Point>> contours6;

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    vector<Vec4i> hierarchy6;

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    findContours(thresh2, contours6, hierarchy6, RETR_TREE, CHAIN_APPROX_NONE);

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    Mat image_copy7 = image2.clone();

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    drawContours(image_copy7, contours6, -1, Scalar(0, 255, 0), 2);

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    imshow("EXTERNAL", image_copy7);

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    waitKey(0);

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    imwrite("contours_retr_tree.jpg", image_copy7);

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    destroyAllWindows();

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}

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