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 
#include 
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/calib3d/calib3d.hpp"
#include 
#include 
#include 
using namespace cv;
using namespace std;

// We need 4 corresponding 2D points(x,y) to calculate homography.
vector left_image;      // Stores 4 points(x,y) of the logo image. Here the four points are 4 corners of image.
vector 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;
}

效果图如下：