Mat getPerspectiveTransform(const Point2f* src, const Point2f* dst)
// Calculate a perspective transform from four pairs of the corresponding points.
// src – Coordinates of quadrangle vertices in the source image.
// dst – Coordinates of the corresponding quadrangle vertices in the destination image.void warpPerspective(InputArray src, OutputArray dst, InputArray M, Size dsize, int flags=INTER_LINEAR, int borderMode=BORDER_CONSTANT, const Scalar& borderValue=Scalar())
// Apply a perspective transform to an image.
// src – Source image.
// dst – Destination image that has the size dsize and the same type as src.
// M – 3*3 transformation matrix.
// dsize – Size of the destination image.
// flags – Combination of interpolation methods and the optional flag WARP_INVERSE_MAP that means that M is the inverse transformation (dstsrc).
// borderMode – Pixel extrapolation method. When borderMode=BORDER_TRANSPARENT, it means that the pixels in the destination image that corresponds to the “outliers” in the source image are not modified by the function.
// borderValue – Value used in case of a constant border. By default, it is 0.

#include <iostream>#include "highgui.h"
#include "opencv2/imgproc/imgproc.hpp"int main()
{// get original image.cv::Mat originalImage = cv::imread("road.png");// perspective image.cv::Mat perspectiveImage;// perspective transformcv::Point2f objectivePoints[4], imagePoints[4];// original image points.imagePoints[0].x = 10.0; imagePoints[0].y = 457.0;imagePoints[1].x = 395.0; imagePoints[1].y = 291.0;imagePoints[2].x = 624.0; imagePoints[2].y = 291.0;imagePoints[3].x = 1000.0; imagePoints[3].y = 457.0;// objective points of perspective image.// move up the perspective image : objectivePoints.y - value .// move left the perspective image : objectivePoints.x - value.double moveValueX = 0.0;double moveValueY = 0.0;objectivePoints[0].x = 46.0 + moveValueX; objectivePoints[0].y = 920.0 + moveValueY;objectivePoints[1].x = 46.0 + moveValueX; objectivePoints[1].y = 100.0 + moveValueY;objectivePoints[2].x = 600.0 + moveValueX; objectivePoints[2].y = 100.0 + moveValueY;objectivePoints[3].x = 600.0 + moveValueX; objectivePoints[3].y = 920.0 + moveValueY;cv::Mat transform = cv::getPerspectiveTransform(objectivePoints, imagePoints);// perspective.cv::warpPerspective(originalImage,perspectiveImage,transform,cv::Size(originalImage.rows, originalImage.cols),cv::INTER_LINEAR | cv::WARP_INVERSE_MAP);// cv::imshow("perspective image", perspectiveImage);// cvWaitKey(0);cv::imwrite("perspectiveImage.png", perspectiveImage);return 0;
}