opencv四点投影变换

// opencv实现投影变换
// 2015 - 09 - 05 create by hym
// 在屏幕上依次点四个点(左上->左下->右下->右上)，再点击屏幕上任意一点即可

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/calib3d/calib3d.hpp"
#include <iostream>
#include <limits>
#include <numeric>
using namespace cv;
using namespace std;

// We need 4 corresponding 2D points(x,y) to calculate homography.
vector<Point2f> left_image;      // Stores 4 points(x,y) of the logo image. Here the four points are 4 corners of image.
vector<Point2f> right_image;    // stores 4 points that the user clicks(mouse left click) in the main image.

// Image containers for main and logo image
Mat imageMain;
Mat imageLogo;

// Function to add main image and transformed logo image and show final output.
// Icon image replaces the pixels of main image in this implementation.
void showFinal(Mat src1, Mat src2)
{

Mat gray, gray_inv, src1final, src2final;
cvtColor(src2, gray, CV_BGR2GRAY);
threshold(gray, gray, 0, 255, CV_THRESH_BINARY);
//adaptiveThreshold(gray,gray,255,ADAPTIVE_THRESH_MEAN_C,THRESH_BINARY,5,4);
bitwise_not(gray, gray_inv);
src1.copyTo(src1final, gray_inv);
src2.copyTo(src2final, gray);
Mat finalImage = src1final + src2final;
namedWindow("output", WINDOW_AUTOSIZE);
imshow("output", finalImage);
cvWaitKey(0);

}

// Here we get four points from the user with left mouse clicks.
// On 5th click we output the overlayed image.
void on_mouse(int e, int x, int y, int d, void *ptr)
{
if (e == EVENT_LBUTTONDOWN)
{
if (right_image.size() < 4)
{

right_image.push_back(Point2f(float(x), float(y)));
cout << x << " " << y << endl;
}
else
{
cout << " Calculating Homography " << endl;
// Deactivate callback
cv::setMouseCallback("Display window", NULL, NULL);
// once we get 4 corresponding points in both images calculate homography matrix
Mat H = findHomography(left_image, right_image, 0);
Mat logoWarped;
// Warp the logo image to change its perspective
warpPerspective(imageLogo, logoWarped, H, imageMain.size());
showFinal(imageMain, logoWarped);

}

}
}

int main(int argc, char** argv)
{
//  We need tow argumemts. "Main image" and "logo image"
/*
if (argc != 3)
{
cout << " Usage: error" << endl;
return -1;
}
*/

// Load images from arguments passed.
imageMain = imread("pai.jpg");
imageLogo = imread("2.3.jpg");
// Push the 4 corners of the logo image as the 4 points for correspondence to calculate homography.
left_image.push_back(Point2f(float(0), float(0)));
left_image.push_back(Point2f(float(0), float(imageLogo.rows)));
left_image.push_back(Point2f(float(imageLogo.cols), float(imageLogo.rows)));
left_image.push_back(Point2f(float(imageLogo.cols), float(0)));

namedWindow("Display window", WINDOW_AUTOSIZE);// Create a window for display.
imshow("Display window", imageMain);

setMouseCallback("Display window", on_mouse, NULL);

//  Press "Escape button" to exit
while (1)
{
int key = cvWaitKey(10);
if (key == 27) break;
}

return 0;
}