OpenCV--C++图像的几何变换（缩放、翻转、仿射/透视变换）

#include
#include
using namespace std;
using namespace cv;
#include

int main()
{
	Mat img = imread("colors.jpg");
	if (img.empty()) {
		cout << "图像读取失败" << endl;
		return -1;
	};

	Mat src, small_img, near, linear, cubic;
	resize(img, small_img, Size(200, 200), 0, 0, INTER_AREA);  //将图像变小
	imshow("small_img", small_img);

	resize(small_img, near, Size(800, 800), 0, 0, INTER_NEAREST);  //最近邻插值
	resize(small_img, linear, Size(800, 800), 0, 0, INTER_LINEAR); //线性插值
	resize(small_img, cubic, Size(800, 800), 0, 0, INTER_CUBIC);   //立方插值
	
	imshow("near", near); //展示不同插值方式放大图像的效果
	imshow("linear", linear);
	imshow("cubic", cubic);
	waitKey(0);
	return 0;
}

#include
#include

using namespace std;
using namespace cv;

int main()
{
	Mat img = imread("colors.jpg");
	if (img.empty()) {
		cout << "图片读取失败" << endl;
		return -1;
	}

	Mat h_flip, v_flip, hv_flip;
	flip(img, h_flip, 0);  //水平翻转
	flip(img, v_flip, 1);  //垂直翻转
	flip(img, hv_flip, -1); //先水平翻转再竖直翻转

	vectorout;  //并排展示翻转的结果
	Mat result;
	out.push_back(h_flip);
	out.push_back(v_flip);
	out.push_back(hv_flip);
	hconcat(out, result);
	imshow("out", result);

	waitKey(0);

	return 0;
}

#include
#include

using namespace std;
using namespace cv;

int main()
{
	Mat img = imread("colors.jpg");
	if (img.empty()) {
		cout << "图像读取失败" << endl;
		return -1;
	}

	Size dst_size(img.rows, img.cols); //设置输出图像的的大小

	// -------------根据旋转角度变换------------------
	double angle = 45;
	Point2f center(img.rows / 2.0, img.cols / 2.0); //设置旋转中心
	Mat r_mat1 = getRotationMatrix2D(center, angle, 1); //计算放射变换的矩阵
	Mat warp1;
	warpAffine(img,warp1, r_mat1,  dst_size);  //进行仿射变换(此处为旋转45°)
	imshow("warp1", warp1);


	//--------------根据定义的3个点进行变换-------------
	Point2f src_p[3];
	Point2f dst_p[3];

	//原图上的3个点
	src_p[0] = Point2f(0, 0);
	src_p[1] = Point2f(0, (float)(img.cols - 10));
	src_p[2] = Point2f((float)(img.rows - 10), (float)(img.cols - 10));

	//原图上3个点在目标图中的位置
	dst_p[0] = Point2f((float)(img.rows) * 0.1, (float)(img.cols) * 0.2);
	dst_p[1] = Point2f((float)(img.rows) * 0.15, (float)(img.cols) * 0.7);
	dst_p[2] = Point2f((float)(img.rows) * 0.8, (float)(img.cols) * 0.9);

	Mat r_mat2, warp2;
	r_mat2 = getAffineTransform(src_p, dst_p);  //根据对应的点求变换矩阵	
	cout << "变换矩阵为：" << r_mat2 << endl;
	warpAffine(img, warp2, r_mat2, dst_size);  //通过变换矩阵进行仿射变换
	imshow("warp2", warp2);



	waitKey(0);

	return 0;
}

#include
#include
using namespace std;
using namespace cv;


int main()
{
	Mat img = imread("colors.jpg");
	if (img.empty()) {
		cout << "图像读取失败" << endl;
		return -1;
	}

	Point2f src_p[4], dst_p[4];
	src_p[0] = Point2f(200, 300);  //原图中的四个点
	src_p[1] = Point2f(300, 600);
	src_p[2] = Point2f(600, 800);
	src_p[3] = Point2f(800, 800);

	dst_p[0] = Point2f(10, 800);  //原图中的四个点对应到变换后的的坐标位置
	dst_p[1] = Point2f(800, 200);
	dst_p[2] = Point2f(600, 100);
	dst_p[3] = Point2f(500, 10);

	Mat r_mat = getPerspectiveTransform(src_p, dst_p); //通过对应的点找到两者之间的变换矩阵
	Mat result;
	warpPerspective(img, result, r_mat, img.size());   // 进行透视变换
	imshow("img", img);
	imshow("result", result);


	waitKey(0);
	return 0;

}

参考资料：

《OpenCV4快速入门》

GitHub - fengzhenHIT/learnOpenCV4: OpenCV 4相关文件