The template matching code is as follows.
#include <iostream> #include <string> #include <vector> #include <stdio.h> #include <opencv2/core/core.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/features2d/features2d.hpp> #include <opencv2/nonfree/features2d.hpp> #include <opencv2/legacy/legacy.hpp> #include "opencv2/video/tracking.hpp" using namespace cv; using namespace std; string intToString(int number) { std::stringstream ss; ss << number; return ss.str(); } class Symbol { public: Mat img; string name; }; void sortCorners(std::vector<cv::Point2f>& corners, cv::Point2f center) { std::vector<cv::Point2f> top, bot; for (unsigned int i = 0; i < corners.size(); i++) { if (corners[i].y < center.y) top.push_back(corners[i]); else bot.push_back(corners[i]); } cv::Point2f tl = top[0].x > top[1].x ? top[1] : top[0]; cv::Point2f tr = top[0].x > top[1].x ? top[0] : top[1]; cv::Point2f bl = bot[0].x > bot[1].x ? bot[1] : bot[0]; cv::Point2f br = bot[0].x > bot[1].x ? bot[0] : bot[1]; corners.clear(); corners.push_back(tl); corners.push_back(tr); corners.push_back(br); corners.push_back(bl); } int readRefImages(Symbol *symbols) { symbols[0].img = imread("arrowL.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[0].img.data) return -1; threshold(symbols[0].img, symbols[0].img, 100, 255, 0); symbols[0].name = "Left 90"; symbols[1].img = imread("arrowR.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[1].img.data) return -1; threshold(symbols[1].img, symbols[1].img, 100, 255, 0); symbols[1].name = "Right 90"; symbols[2].img = imread("arrowT.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[2].img.data) return -1; threshold(symbols[2].img, symbols[2].img, 100, 255, 0); symbols[2].name = "Turn Around"; symbols[3].img = imread("arrowB.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[3].img.data) return -1; threshold(symbols[3].img, symbols[3].img, 100, 255, 0); symbols[3].name = "Ball"; symbols[4].img = imread("arrowL45.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[4].img.data) return -1; threshold(symbols[4].img, symbols[4].img, 100, 255, 0); symbols[4].name = "Left 45"; symbols[5].img = imread("arrowR45.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[5].img.data) return -1; threshold(symbols[5].img, symbols[5].img, 100, 255, 0); symbols[5].name = "Right 45"; symbols[6].img = imread("arrowStop.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[6].img.data) return -1; threshold(symbols[6].img, symbols[6].img, 100, 255, 0); symbols[6].name = "Stop"; symbols[7].img = imread("arrowGo.jpg", CV_LOAD_IMAGE_GRAYSCALE); if (!symbols[7].img.data) return -1; threshold(symbols[7].img, symbols[7].img, 100, 255, 0); symbols[7].name = "Go"; return 0; } int lowThreshold; void CannyThreshold(int, void*) { } int main(int argc, char** argv) { // check http://docs.opencv.org/doc/tutorials/features2d/table_of_content_features2d/table_of_content_features2d.html // for OpenCV general detection/matching framework details VideoCapture cap; cap.open(0); namedWindow("A", CV_WINDOW_AUTOSIZE); namedWindow("B", CV_WINDOW_AUTOSIZE); namedWindow("C", CV_WINDOW_AUTOSIZE); Mat camera; Mat greyImg; Symbol symbols[10]; if (readRefImages(symbols) == -1) { printf("Error reading reference symbols\n"); return -1; } createTrackbar("Min Threshold:", "A", &lowThreshold, 100, CannyThreshold); double t = (double) getTickCount(); // do something ... //t = ((double)getTickCount() - t)/getTickFrequency(); //cout << "Times passed in seconds: " << t << endl; cap >> camera; Mat new_image; while (1) { t = (double) getTickCount() - t; cap >> camera; cvtColor(camera, greyImg, CV_RGB2GRAY); //threshold(greyImg, greyImg, 100, 255, 0); Mat canny_output; vector<vector<Point> > contours; vector<Vec4i> hierarchy; GaussianBlur(greyImg, greyImg, Size(9, 9), 2, 2); /// Detect edges using canny Canny(greyImg, canny_output, lowThreshold, lowThreshold * 3, 3); // imshow("B",canny_output); /// Find contours findContours(canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0)); vector<Point> approxRect; for (size_t i = 0; i < contours.size(); i++) { approxPolyDP(contours[i], approxRect, arcLength(Mat(contours[i]), true) * 0.05, true); if (approxRect.size() == 4) { float area = contourArea(contours[i]); if (area > 10000) { std::vector<cv::Point2f> corners; vector<Point>::iterator vertex; vertex = approxRect.begin(); //vertex++; circle(camera, *vertex, 2, Scalar(0, 0, 255), -1, 8, 0); corners.push_back(*vertex); vertex++; circle(camera, *vertex, 2, Scalar(0, 0, 255), -1, 8, 0); corners.push_back(*vertex); vertex++; circle(camera, *vertex, 2, Scalar(0, 0, 255), -1, 8, 0); corners.push_back(*vertex); vertex++; circle(camera, *vertex, 2, Scalar(0, 0, 255), -1, 8, 0); corners.push_back(*vertex); Moments mu; mu = moments(contours[i], false); Point2f center(mu.m10 / mu.m00, mu.m01 / mu.m00); sortCorners(corners, center); // Define the destination image Mat correctedImg = ::Mat::zeros(195, 271, CV_8UC3); // Corners of the destination image std::vector<cv::Point2f> quad_pts; quad_pts.push_back(Point2f(0, 0)); quad_pts.push_back(Point2f(correctedImg.cols, 0)); quad_pts.push_back( Point2f(correctedImg.cols, correctedImg.rows)); quad_pts.push_back(Point2f(0, correctedImg.rows)); // Get transformation matrix Mat transmtx = getPerspectiveTransform(corners, quad_pts); // Apply perspective transformation warpPerspective(camera, correctedImg, transmtx, correctedImg.size()); Mat correctedImgBin; cvtColor(correctedImg, correctedImgBin, CV_RGB2GRAY); //equalizeHist(correctedImgBin, correctedImgBin); correctedImgBin.copyTo(new_image); threshold(correctedImgBin, correctedImgBin, 140, 255, 0); imshow("B", correctedImgBin); double minVal,maxVal,medVal; minMaxLoc(new_image, &minVal, &maxVal); medVal=(maxVal-minVal)/2; threshold(new_image, new_image, medVal, 255, 0); imshow("C", new_image); Mat diffImg; int match, minDiff, diff; minDiff = 12000; match = -1; for (int i = 0; i < 8; i++) { //diffImg = symbols[i].img-correctedImgBin; bitwise_xor(new_image, symbols[i].img, diffImg, noArray()); diff = countNonZero(diffImg); if (diff < minDiff) { minDiff = diff; match = i; } if (i == 0) { // imshow("B",diffImg); } } //imshow("B", correctedImg); if (match != -1) { putText(camera, symbols[match].name, Point(320, 30), 1, 2, Scalar(0, 255, 0), 2); } //break; } } } imshow("A", camera); waitKey(20); } }