opencv C++极坐标变换

#include<opencv2/core/core.hpp>
#include<opencv2/highgui/highgui.hpp>
#include<opencv2/imgproc/imgproc.hpp>
#include<iostream>

// center:极坐标的变换中心
// minr:变换中心的最小距离
// mintheta:最小距离
// thetaStep:角度的变换步长
// rStep:距离的变换步长
cv::Mat polar(cv::Mat I,cv::Point2f center,cv::Size size,float minr=0,float mintheta=0,float thetaStep=1.0/4,float rStep=1.0){
    cv::Mat ri=cv::Mat::zeros(cv::Size(1,size.height),CV_32FC1);
    for(int i=0;i<size.height;++i)
        ri.at<float>(i,0)=minr+i*rStep;
    cv::Mat r=cv::repeat(ri,1,size.width);
    cv::Mat thetaj=cv::Mat::zeros(cv::Size(size.width,1),CV_32FC1);
    for(int i=0;i<size.width;++i)
        thetaj.at<float>(0,i)=mintheta+i*thetaStep;
    cv::Mat theta=cv::repeat(thetaj,size.height,1);
    cv::Mat x,y;
    cv::polarToCart(r,theta,x,y,true);
    x+=center.x;
    y+=center.y;
    cv::Mat dst =125*cv::Mat::ones(size,CV_8UC1);
    for(int i=0;i<size.height;++i){
        for(int j=0;j<size.width;++j){
            float xij=x.at<float>(i,j);
            float yij=y.at<float>(i,j);
            int nearestx=int(round(xij));
            int nearesty=int(round(yij));
            if((0<=nearestx&&nearestx<I.cols)&&(0<=nearesty&&nearesty<I.rows))
                dst.at<uchar>(i,j)=I.at<uchar>(nearesty,nearestx);
        }
    }
    return dst;
}


int main(){
    cv::Mat I=cv::imread("/home/nan/图片/openimage/circleWithText.jpg",cv::IMREAD_GRAYSCALE);
    if(!I.data) return -1;
    float thetaStep=1.0/4;  // thetaStep=0.25代表整个圆环，thetaStep=0.5代表半个圆环，thetaStep=1代表1/4个圆环。
    float minr=55;
    cv::Size size (int(360/thetaStep),50);  //50:圆环文字的大致高度。
    // 圆环角度范围为(0,360),输出圆环图像的宽度为(360/thetaStep):
    cv::Mat dst=polar(I,cv::Point2f(110,109),size,minr);
    //cv::imshow("极坐标变换0:",dst);
    cv::flip(dst,dst,0);  // 0 meansflipping around the x-axis and positive value (for example, 1) means
    // flipping around y-axis. Negative value (for example, -1) means flipping around both axes.
    cv::imshow("I",I);
    cv::imshow("最近邻插值极坐标变换:",dst);

    cv::linearPolar(I,dst,cv::Point2f(110,109),100,cv::INTER_LINEAR);
    cv::imshow("线性插值极坐标变换:",dst);

    cv::logPolar(I,dst,cv::Point2f(110,109),40,cv::WARP_FILL_OUTLIERS);
    cv::imshow("对数极坐标变换:",dst);
    //cv::InterpolationFlags
    cv::waitKey(0);
    return 0;
}

来源：https://www.cnblogs.com/ligei/p/11529031.html