samples/cpp/polar_transforms.cpp

An example using the cv::linearPolar and cv::logPolar operations

#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/videoio.hpp"
#include <iostream>
 
using namespace cv;
 
int main( int argc, char** argv )
{
 VideoCapture capture;
 Mat log_polar_img, lin_polar_img, recovered_log_polar, recovered_lin_polar_img;
 
 CommandLineParser parser(argc, argv, "{@input|0| camera device number or video file path}");
 parser.about("\nThis program illustrates usage of Linear-Polar and Log-Polar image transforms\n");
 parser.printMessage();
 std::string arg = parser.get<std::string>("@input");
 
 if( arg.size() == 1 && isdigit(arg[0]) )
 capture.open( arg[0] - '0' );
 else
 capture.open(samples::findFileOrKeep(arg));
 
 if( !capture.isOpened() )
 {
 fprintf(stderr,"Could not initialize capturing...\n");
 return -1;
 }
 
 namedWindow( "Linear-Polar", WINDOW_AUTOSIZE );
 namedWindow( "Log-Polar", WINDOW_AUTOSIZE);
 namedWindow( "Recovered Linear-Polar", WINDOW_AUTOSIZE);
 namedWindow( "Recovered Log-Polar", WINDOW_AUTOSIZE);
 
 moveWindow( "Linear-Polar", 20,20 );
 moveWindow( "Log-Polar", 700,20 );
 moveWindow( "Recovered Linear-Polar", 20, 350 );
 moveWindow( "Recovered Log-Polar", 700, 350 );
 int flags = INTER_LINEAR + WARP_FILL_OUTLIERS;
 Mat src;
 for(;;)
 {
 capture >> src;
 
 if(src.empty() )
 break;
 
 Point2f center( (float)src.cols / 2, (float)src.rows / 2 );
 double maxRadius = 0.7*min(center.y, center.x);
 
#if 0 //deprecated
 double M = frame.cols / log(maxRadius);
 logPolar(frame, log_polar_img, center, M, flags);
 linearPolar(frame, lin_polar_img, center, maxRadius, flags);
 
 logPolar(log_polar_img, recovered_log_polar, center, M, flags + WARP_INVERSE_MAP);
 linearPolar(lin_polar_img, recovered_lin_polar_img, center, maxRadius, flags + WARP_INVERSE_MAP);
#endif
 // direct transform
 warpPolar(src, lin_polar_img, Size(),center, maxRadius, flags); // linear Polar
 warpPolar(src, log_polar_img, Size(),center, maxRadius, flags + WARP_POLAR_LOG); // semilog Polar
 // inverse transform
 warpPolar(lin_polar_img, recovered_lin_polar_img, src.size(), center, maxRadius, flags + WARP_INVERSE_MAP);
 warpPolar(log_polar_img, recovered_log_polar, src.size(), center, maxRadius, flags + WARP_POLAR_LOG + WARP_INVERSE_MAP);
 
 // Below is the reverse transformation for (rho, phi)->(x, y) :
 Mat dst;
 if (flags & WARP_POLAR_LOG)
 dst = log_polar_img;
 else
 dst = lin_polar_img;
 //get a point from the polar image
 int rho = cvRound(dst.cols * 0.75);
 int phi = cvRound(dst.rows / 2.0);
 
 double angleRad, magnitude;
 double Kangle = dst.rows / CV_2PI;
 angleRad = phi / Kangle;
 if (flags & WARP_POLAR_LOG)
 {
 double Klog = dst.cols / std::log(maxRadius);
 magnitude = std::exp(rho / Klog);
 }
 else
 {
 double Klin = dst.cols / maxRadius;
 magnitude = rho / Klin;
 }
 int x = cvRound(center.x + magnitude * cos(angleRad));
 int y = cvRound(center.y + magnitude * sin(angleRad));
 drawMarker(src, Point(x, y), Scalar(0, 255, 0));
 drawMarker(dst, Point(rho, phi), Scalar(0, 255, 0));
 
 imshow("Src frame", src);
 imshow("Log-Polar", log_polar_img);
 imshow("Linear-Polar", lin_polar_img);
 imshow("Recovered Linear-Polar", recovered_lin_polar_img );
 imshow("Recovered Log-Polar", recovered_log_polar );
 
 if( waitKey(10) >= 0 )
 break;
 }
 return 0;
}