opencv 透視變換（一） — 求兩幅圖像上對應四個點的透視變換矩陣

opencv 通過透視變換可以將圖像的整體或部分進行映射處理，實現其它的視覺效果。透視變換矩陣是核心，這裏給出如何根據兩幅圖像對應區域計算透視變換矩陣，以實現透視變換。可以用到相機標定等處理中。

兩種選點計算方式。

1、手動選點輸入計算

#include<iostream>
#include<opencv2/opencv.hpp>
#include "opencv2/features2d.hpp"
using namespace cv;
using namespace std;


int main()
{
	Mat imgc = imread("D:/cal/c.jpg");
	Mat imge = imread("D:/cal/e.jpg");

	vector<Point2f> c_corners(4);
	c_corners[0] = Point2f(246, 249);
	c_corners[1] = Point2f(489, 649);
	c_corners[2] = Point2f(587, 491);
	c_corners[3] = Point2f(424, 69);

	vector<Point2f> e_corners(4);		//src點對應想放置的位置。例如旋轉
	e_corners[0] = Point2f(348, 238);
	e_corners[1] = Point2f(576, 585);
	e_corners[2] = Point2f(661, 440);
	e_corners[3] = Point2f(496, 66);

	for (int i = 0; i < 4; i++) {
		circle(imgc, c_corners[i], 5, { 0,0,255 }, 5);
		circle(imge, e_corners[i], 5, { 0,255,0 }, 5);
	}
	namedWindow("imgc", WINDOW_KEEPRATIO);	imshow("imgc", imgc);//觀察src.dst示意圖
	namedWindow("imge", WINDOW_KEEPRATIO);	imshow("imge", imge);

	/*-----------------------------------------	獲取矩陣	--------------------------------------------------------------*/
	Mat transform_M = getPerspectiveTransform(c_corners, e_corners);
	cout << transform_M << endl;

	waitKey();
	return 0;
}

 

 

2、鼠標點擊取兩幅圖像對應點

#include <opencv2/opencv.hpp>
using namespace cv;
using namespace std;

struct userdata
{
	Mat img;
	vector<Point2f> points;
};

void mouseHandler(int event, int x, int y, int flags, void* data_ptr)
{
	if (event == EVENT_LBUTTONDOWN)
	{
		userdata* data = ((userdata*)data_ptr);
		circle(data->img, Point(x, y), 3, Scalar(0, 255, 255), 5);
		namedWindow("Image_window", 0); setWindowProperty("Image_window", WND_PROP_FULLSCREEN, WINDOW_FULLSCREEN); imshow("Image_window", data->img);

		if (data->points.size() < 4)
		{
			data->points.push_back(Point2f(x, y));
		}
	}
}

int main(int argc, char** argv)
{
	Mat im_c = imread("D:/cal/c.jpg");
	userdata data_c;
	data_c.img = im_c;
	namedWindow("Image_window", 0); setWindowProperty("Image_window", WND_PROP_FULLSCREEN, WINDOW_FULLSCREEN); imshow("Image_window", im_c);
	setMouseCallback("Image_window", mouseHandler, &data_c);
	waitKey(0);

	Mat im_e = imread("D:/cal/e.jpg");
	userdata data_e;
	data_e.img = im_e;
	namedWindow("Image_window", 0); setWindowProperty("Image_window", WND_PROP_FULLSCREEN, WINDOW_FULLSCREEN);  imshow("Image_window", im_e);
	setMouseCallback("Image_window", mouseHandler, &data_e);
	waitKey(0);

	Mat warpMatrix = getPerspectiveTransform(data_e.points, data_c.points);

	cout << "warpMatrix=  " << warpMatrix << endl;

	getchar();
	return 0;
}

鼠標取點會更方便一些。