contour

// // Created by yuqiong on 3/2/19. // test drawing countours and then min bounding boxes // #include "opencv2/imgcodecs.hpp" #include "opencv2/highgui.hpp" #include "opencv2/imgproc.hpp" #include <iostream> using namespace cv; using namespace std; Mat src_gray; int thresh = 100; RNG rng(12345); void thresh_callback(int, void* ); int main( int argc, char** argv ) { CommandLineParser parser( argc, argv, "{@input | ../data/stuff.jpg | input image}" ); Mat src = imread( parser.get<String>( "@input" ) ); if( src.empty() ) { cout << "Could not open or find the image!\n" << endl; cout << "usage: " << argv[0] << " <Input image>" << endl; return -1; } cvtColor( src, src_gray, COLOR_BGR2GRAY ); blur( src_gray, src_gray, Size(3,3) ); const char* source_window = "Source"; namedWindow( source_window ); imshow( source_window, src ); const int max_thresh = 255; createTrackbar( "Canny thresh:", source_window, &thresh, max_thresh, thresh_callback ); thresh_callback( 0, 0 ); waitKey(); return 0; } void thresh_callback(int, void* ) { // binarize grayscale image to binary image as to get simpler contour Mat binary_output; threshold(src_gray, binary_output, 5, 255, THRESH_BINARY); imshow("Binary output", binary_output); vector<vector<Point> > contours; findContours( binary_output, contours, RETR_TREE, CHAIN_APPROX_SIMPLE ); vector<vector<Point> > contours_poly(contours.size()); // store polygons for contours // vector<Rect> rectangles(contours.size()); // stores bounding boxes vector<RotatedRect> rectangles(contours.size()); // stores bounding boxes // Rect minBoundRect; // minimum bounding box RotatedRect minBoundRect; // minimum bounding box // loop through and find smallest bounding boxes float min_width = 0; float min_height = 0; int min_square_idx = 0; std::cout << "Contour numbers " << contours.size() << std::endl; for (size_t i = 0; i < contours.size(); i++) { // https://docs.opencv.org/3.4/da/d0c/tutorial_bounding_rects_circles.html approxPolyDP(contours[i], contours_poly[i], 3, true ); // Rect rectangle = boundingRect(contours_poly[i]); RotatedRect rectangle = minAreaRect(contours_poly[i]); rectangles[i] = rectangle; // Store the index position of the minimum square found if ((rectangle.size.width <= min_width) && (rectangle.size.height <= min_height)) { min_width = rectangle.size.width; min_height = rectangle.size.height; min_square_idx = i; } } minBoundRect = rectangles[min_square_idx]; Point2f rect_points[4]; // get rotated rectangle points minBoundRect.points( rect_points ); Point2f dst_points[4]; // destination points anchors Point2f tl(0, 255); dst_points[0] = tl; Point2f bl(0, 0); dst_points[1] = bl; Point2f br(255, 0); dst_points[2] = br; Point2f tr(255, 255); dst_points[3] = tr; Mat M = getPerspectiveTransform(rect_points, dst_points); // translation matrix Mat wrapped; Size wrapped_size(256, 256); warpPerspective(src_gray, wrapped, M, wrapped_size); imshow("Wrapped binary output", wrapped); // Write to file! FileStorage out_file("test.xml", FileStorage::WRITE); out_file << "trans" << M; out_file.release(); // Read it back FileStorage in_file("test.xml", FileStorage::READ); Mat file_matrix; in_file["trans"] >> file_matrix; cout << file_matrix << endl; in_file.release(); // now test invert Mat invert; Size invert_size(256, 256); warpPerspective(wrapped, invert, file_matrix, invert_size, WARP_INVERSE_MAP); imshow("Read back", invert); }