标签：不能 mic png arp war 特殊 nbsp 矩阵 旋转
仿射变换保证物体形状的“平直性”和“平行性”。透视变换不能保证物体形状的“平行性”。仿射变换是透视变换的特殊形式。
将透视变换写成3*3矩阵形式，即为M;
以下面这张图为例，实现仿射变换，包括旋转，平移，缩放，剪切，以图像中心为变换中心；
仿射变换
旋转（逆时针旋转30度）
Mat M=Mat::eye(3,3, CV_32FC1);
float alpha=PI/6;
float tx=0;
float ty=0;
float scale=1;
M.at<float>(0, 0) = cos(alpha);
M.at<float>(0, 1) = sin(alpha);
M.at<float>(0, 2) = (1-cos(alpha))*center.x - sin(alpha)* center.y;
M.at<float>(1, 0) = -sin(alpha);
M.at<float>(1, 1) = cos(alpha);
M.at<float>(1, 2) = sin(alpha)* center.x +(1-cos(alpha))*center.y;
M.at<float>(2, 0) = 0;
M.at<float>(2, 1) = 0;
M.at<float>(2, 2) = 1;
平移（水平和垂直方向各向右平移20个像素）
Mat M=Mat::eye(3,3, CV_32FC1); float alpha=0; float tx=20; float ty=20; float scale=0; M.at<float>(0, 0) = cos(alpha); M.at<float>(0, 1) = sin(alpha); M.at<float>(0, 2) = (1-cos(alpha))*center.x - sin(alpha)* center.y + tx; M.at<float>(1, 0) = -sin(alpha); M.at<float>(1, 1) = cos(alpha); M.at<float>(1, 2) = sin(alpha)* center.x +(1-cos(alpha))*center.y + ty; M.at<float>(2, 0) = 0; M.at<float>(2, 1) = 0; M.at<float>(2, 2) = 1;
缩放（图像缩小1/2）
Mat M=Mat::eye(3,3, CV_32FC1); float alpha=0; float tx=0; float ty=0; float scale=0.5; M.at<float>(0, 0) = cos(alpha) * scale; M.at<float>(0, 1) = sin(alpha) * scale; M.at<float>(0, 2) = (1-cos(alpha)* scale)*center.x - sin(alpha)* center.y* scale + tx; M.at<float>(1, 0) = -sin(alpha) * scale; M.at<float>(1, 1) = cos(alpha)* scale; M.at<float>(1, 2) = sin(alpha)* center.x* scale +(1-cos(alpha)* scale)*center.y + ty; M.at<float>(2, 0) = 0; M.at<float>(2, 1) = 0; M.at<float>(2, 2) = 1;
错切变换（剪切变换）：
Mat M=Mat::eye(3,3, CV_32FC1); float alpha=PI/12; float tx=0; float ty=0; float scale=1; M.at<float>(0, 0) = 1; M.at<float>(0, 1) = sin(alpha); M.at<float>(0, 2) = (1-cos(alpha))*center.x - sin(alpha)* center.y; M.at<float>(1, 0) = 0; M.at<float>(1, 1) = 1; M.at<float>(1, 2) = sin(alpha)* center.x +(1-cos(alpha))*center.y; M.at<float>(2, 0) = 0; M.at<float>(2, 1) = 0; M.at<float>(2, 2) = 1;
透视变换（透视变换不保证平行性）
Mat M=Mat::eye(3,3, CV_32FC1); float alpha=0; float tx=0; float ty=0; float scale=1; M.at<float>(0, 0) = cos(alpha); M.at<float>(0, 1) = sin(alpha); M.at<float>(0, 2) =(1-cos(alpha))*center.x - sin(alpha)* center.y + tx; M.at<float>(1, 0) = -sin(alpha); M.at<float>(1, 1) = cos(alpha); M.at<float>(1, 2) =sin(alpha)* center.x +(1-cos(alpha))*center.y + ty; M.at<float>(2, 0) = 0.001; M.at<float>(2, 1) = 0.001; M.at<float>(2, 2) = 1;
上述操作使用同一个opencv接口函数：warpPerspective(srcImg, dstImg, M, Size(width, height));
标签：不能 mic png arp war 特殊 nbsp 矩阵 旋转
原文地址：http://www.cnblogs.com/riddick/p/7398311.html
