背景：
平时在拍照片时难免不小心把照片拍歪了，这时候可以使用透视变换矫正拍歪的照片！
环境：
运行环境：Win10 x64
OpenCV 版本：4.5.1
源代码：
/******************************************************************************* @brief : 使用透视变换矫正图片* @usage : 用鼠标在原图上依次点击 左上-> 右上->右下->左下四个角点，*然后按回车，即可得的变换后的图像，变换后的图像会自动保存* @author: QiDianMaker*****************************************************************************/#include <iostream>#include <string>#include <cmath>#include <opencv2/opencv.hpp>using Points = cv::Point2f[4];// 全局变量Points src_points;Points dst_points;cv::Mat src, dst;// 鼠标回调函数声明void on_mouse(int event, int x, int y, int flags, void* ustc);int main(){const std::string image_name{ "image.jpg" };::src = cv::imread(image_name);if (src.empty()) {std::cerr << "could not load image...\n";return -1;}cv::Mat src_copy;::src.copyTo(src_copy);cv::namedWindow("Input", cv::WINDOW_AUTOSIZE);cv::setMouseCallback("Input", on_mouse, 0);cv::imshow("Input", ::src);cv::waitKey();// 计算欧式距离auto distance = [](cv::Point2f p1, cv::Point2f p2) -> float {return std::hypotf((p1.x - p2.x), (p1.y - p2.y));};cv::Size2f dst_size(distance(src_points[0], src_points[1]),distance(src_points[1], src_points[2]));std::cout << "dst_size = " << dst_size << std::endl;::dst_points[0] = cv::Point2f(0.0f, 0.0f);::dst_points[1] = cv::Point2f(dst_size.width, 0.0f);::dst_points[2] = cv::Point2f(dst_size.width, dst_size.height);::dst_points[3] = cv::Point2f(0.0f, dst_size.height);// 进行透视变换auto warp_matrix = cv::getPerspectiveTransform(::src_points, ::dst_points);cv::warpPerspective(src_copy, ::dst, warp_matrix, dst_size,cv::INTER_CUBIC, cv::BORDER_CONSTANT);cv::imshow("Output", ::dst);cv::imwrite("./out_" + image_name, ::dst);std::cout << "Save successful!" << std::endl;cv::waitKey();}void on_mouse(int event, int x, int y, int flags, void* ustc){const auto point_color = cv::Scalar(0, 0, 255); // 红色const auto line_color = cv::Scalar(0, 255, 0); // 绿色static int idx = 0;if (event == cv::EVENT_FLAG_LBUTTON) {::src_points[idx] = cv::Point2i(x, y);cv::circle(::src, ::src_points[idx], 2, point_color, 2, 2);std::cout << "Point" << idx + 1 << ": " << src_points[idx] << std::endl;if (idx > 0)cv::line(::src, ::src_points[idx-1], ::src_points[idx], line_color, 2, 2);if (idx == 3)cv::line(::src, ::src_points[3], ::src_points[0], line_color, 2, 2);cv::imshow("Input", ::src);++idx;}}
运行效果：
