#include <iostream>
#include<opencv2/opencv.hpp>
 
using namespace cv;
 
void rotate_arbitrarily_angle(Mat &src,Mat &dst,float angle)
{
    float radian = (float) (angle /180.0 * CV_PI);
 
    //填充圖像
    int maxBorder =(int) (max(src.cols, src.rows)* 1.414 ); //即為sqrt(2)*max
    int dx = (maxBorder - src.cols)/2;
    int dy = (maxBorder - src.rows)/2;
    copyMakeBorder(src, dst, dy, dy, dx, dx, BORDER_CONSTANT);
 
    //旋轉(zhuǎn)
    Point2f center( (float)(dst.cols/2) , (float) (dst.rows/2));
    Mat affine_matrix = getRotationMatrix2D( center, angle, 1.0 );//求得旋轉(zhuǎn)矩陣
    warpAffine(dst, dst, affine_matrix, dst.size());
 
    //計算圖像旋轉(zhuǎn)之后包含圖像的最大的矩形
    float sinVal = abs(sin(radian));
    float cosVal = abs(cos(radian));
    Size targetSize( (int)(src.cols * cosVal +src.rows * sinVal),
                     (int)(src.cols * sinVal + src.rows * cosVal) );
 
    //剪掉多余邊框
    int x = (dst.cols - targetSize.width) / 2;
    int y = (dst.rows - targetSize.height) / 2;
    Rect rect(x, y, targetSize.width, targetSize.height);
    dst = Mat(dst,rect);
}
 
int main() {
    cv::Mat src=cv::imread("../3.png");
    cv::Mat dst;
    rotate_arbitrarily_angle(src,dst,30);
    cv::imshow("src",src);
    cv::imshow("dst",dst);
    cv::waitKey(0);
    return 0;
}

cv::Mat rotate_arbitrarily_angle1(cv::Mat matSrc, float angle, bool direction,int height,int width) {
    float theta = angle * CV_PI / 180.0;
    int nRowsSrc = matSrc.rows;
    int nColsSrc = matSrc.cols; // 如果是順時針旋轉(zhuǎn)
    if (!direction) theta = 2 * CV_PI - theta; // 全部以逆時針旋轉(zhuǎn)來計算
    // 逆時針旋轉(zhuǎn)矩陣
    float matRotate[3][3]{ {
                                   std::cos(theta), -std::sin(theta), 0},
                           {std::sin(theta), std::cos(theta), 0 },
                           {0, 0, 1} };
 
    float pt[3][2]{
            { 0, nRowsSrc },
            {nColsSrc, nRowsSrc},
            {nColsSrc, 0} };
 
    for (int i = 0; i < 3; i++) {
        float x = pt[i][0] * matRotate[0][0] + pt[i][1] * matRotate[1][0];
        float y = pt[i][0] * matRotate[0][1] + pt[i][1] * matRotate[1][1];
        pt[i][0] = x; pt[i][1] = y;
    }
    // 計算出旋轉(zhuǎn)后圖像的極值點和尺寸
    float fMin_x = std::min(std::min(std::min(pt[0][0], pt[1][0]), pt[2][0]), (float)0.0);
    float fMin_y = std::min(std::min(std::min(pt[0][1], pt[1][1]), pt[2][1]), (float)0.0);
    float fMax_x = std::max(std::max(std::max(pt[0][0], pt[1][0]), pt[2][0]), (float)0.0);
    float fMax_y = std::max(std::max(std::max(pt[0][1], pt[1][1]), pt[2][1]), (float)0.0);
    int nRows = cvRound(fMax_y - fMin_y + 0.5) + 1;
    int nCols = cvRound(fMax_x - fMin_x + 0.5) + 1;
    int nMin_x = cvRound(fMin_x + 0.5);
    int nMin_y = cvRound(fMin_y + 0.5);
    // 拷貝輸出圖像
    cv::Mat matRet(nRows, nCols, matSrc.type(), cv::Scalar(0));
    for (int j = 0; j < nRows; j++) {
        for (int i = 0; i < nCols; i++) {
            // 計算出輸出圖像在原圖像中的對應(yīng)點的坐標，然后復(fù)制該坐標的灰度值
            // 因為是逆時針轉(zhuǎn)換，所以這里映射到原圖像的時候可以看成是，輸出圖像
            // 到順時針旋轉(zhuǎn)到原圖像的，而順時針旋轉(zhuǎn)矩陣剛好是逆時針旋轉(zhuǎn)矩陣的轉(zhuǎn)置
            // 同時還要考慮到要把旋轉(zhuǎn)后的圖像的左上角移動到坐標原點。
            int x = (i + nMin_x) * matRotate[0][0] + (j + nMin_y) * matRotate[0][1];
            int y = (i + nMin_x) * matRotate[1][0] + (j + nMin_y) * matRotate[1][1];
            if (x >= 0 && x < nColsSrc && y >= 0 && y < nRowsSrc) {
                matRet.at<uchar>(j, i) = matSrc.at<uchar>(y, x);
            }
        }
    }
    if(direction== false){//當需要順時針旋轉(zhuǎn)回水平位置時   
        int x = (matRet.cols -width) / 2;
        int y = (matRet.rows -height) / 2;
 
        //width和height是水平條件下圖像的寬高   
        cv::Rect rect(x, y, width, height);
        matRet = cv::Mat(matRet,rect);
    }
    return matRet;
}