Homography投影轉換

- 8月 27, 2022

程式碼

#include "opencv2/opencv.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/core.hpp"
#include "opencv2/dnn.hpp"
#include "opencv2/xfeatures2d/nonfree.hpp"
#include "opencv2/features2d/features2d.hpp"
#include <iostream>
#include <fstream> 
#include<cmath>
#include<string>
#include <algorithm>
using namespace std;
using namespace cv;
using namespace cv::dnn;
using namespace cv::xfeatures2d;

int main()
{
	Mat img1 = imread("C:/img/box.png", IMREAD_GRAYSCALE);
	Mat img2 = imread("C:/img/box_in_scene.png", IMREAD_GRAYSCALE);
	if (!img1.data || !img2.data) {
		return -1;
	}
	imshow("object image", img1);
	imshow("object in scene", img2);

	// surf featurs extraction
	int minHessian = 400;
	Ptr<SURF> detector = SURF::create(minHessian);
	vector<KeyPoint> keypoints_obj;
	vector<KeyPoint> keypoints_scene;
	Mat descriptor_obj, descriptor_scene;
	detector->detectAndCompute(img1, Mat(), keypoints_obj, descriptor_obj);
	detector->detectAndCompute(img2, Mat(), keypoints_scene, descriptor_scene);

	// matching
	FlannBasedMatcher matcher;
	vector<DMatch> matches;
	matcher.match(descriptor_obj, descriptor_scene, matches);

	// find good matched points
	double minDist = 1000;
	double maxDist = 0;
	for (int i = 0; i < descriptor_obj.rows; i++) {
		double dist = matches[i].distance;
		if (dist > maxDist) {
			maxDist = dist;
		}
		if (dist < minDist) {
			minDist = dist;
		}
	}
	printf("max distance : %f\n", maxDist);
	printf("min distance : %f\n", minDist);
	vector<DMatch> goodMatches;
	for (int i = 0; i < descriptor_obj.rows; i++) {
		double dist = matches[i].distance;
		if (dist < max(3 * minDist, 0.02)) {
			goodMatches.push_back(matches[i]);
		}
	}

	Mat matchesImg;
	drawMatches(img1, keypoints_obj, img2, keypoints_scene, goodMatches, matchesImg, Scalar::all(-1),
		Scalar::all(-1), vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS
	);

	vector<Point2f> obj;
	vector<Point2f> objInScene;
	for (size_t t = 0; t < goodMatches.size(); t++) {
		obj.push_back(keypoints_obj[goodMatches[t].queryIdx].pt);
		objInScene.push_back(keypoints_scene[goodMatches[t].trainIdx].pt);
	}
	Mat H = findHomography(obj, objInScene, RANSAC);

	vector<Point2f> obj_corners(4);
	vector<Point2f> scene_corners(4);
	obj_corners[0] = Point(0, 0);
	obj_corners[1] = Point(img1.cols, 0);
	obj_corners[2] = Point(img1.cols, img1.rows);
	obj_corners[3] = Point(0, img1.rows);
	perspectiveTransform(obj_corners, scene_corners, H);

	// draw line
	line(matchesImg, scene_corners[0] + Point2f(img1.cols, 0), scene_corners[1] + Point2f(img1.cols, 0), Scalar(0, 0, 255), 2, 8, 0);
	line(matchesImg, scene_corners[1] + Point2f(img1.cols, 0), scene_corners[2] + Point2f(img1.cols, 0), Scalar(0, 0, 255), 2, 8, 0);
	line(matchesImg, scene_corners[2] + Point2f(img1.cols, 0), scene_corners[3] + Point2f(img1.cols, 0), Scalar(0, 0, 255), 2, 8, 0);
	line(matchesImg, scene_corners[3] + Point2f(img1.cols, 0), scene_corners[0] + Point2f(img1.cols, 0), Scalar(0, 0, 255), 2, 8, 0);

	Mat dst;
	cvtColor(img2, dst, COLOR_GRAY2BGR);
	line(dst, scene_corners[0], scene_corners[1], Scalar(0, 0, 255), 2, 8, 0);
	line(dst, scene_corners[1], scene_corners[2], Scalar(0, 0, 255), 2, 8, 0);
	line(dst, scene_corners[2], scene_corners[3], Scalar(0, 0, 255), 2, 8, 0);
	line(dst, scene_corners[3], scene_corners[0], Scalar(0, 0, 255), 2, 8, 0);

	imshow("find known object demo", matchesImg);
	imshow("Draw object", dst);

	waitKey(0);
	return 0;

}