OpenCV  4.0.0-pre
Open Source Computer Vision
polar_transforms.cpp

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

#include <iostream>
using namespace cv;
static void help( void )
{
printf("\nThis program illustrates Linear-Polar and Log-Polar image transforms\n"
"Usage :\n"
"./polar_transforms [[camera number -- Default 0],[path_to_filename]]\n\n");
}
int main( int argc, char** argv )
{
VideoCapture capture;
Mat log_polar_img, lin_polar_img, recovered_log_polar, recovered_lin_polar_img;
help();
CommandLineParser parser(argc, argv, "{@input|0|}");
std::string arg = parser.get<std::string>("@input");
if( arg.size() == 1 && isdigit(arg[0]) )
capture.open( arg[0] - '0' );
else
capture.open( arg.c_str() );
if( !capture.isOpened() )
{
const char* name = argv[0];
fprintf(stderr,"Could not initialize capturing...\n");
fprintf(stderr,"Usage: %s <CAMERA_NUMBER> , or \n %s <VIDEO_FILE>\n", name, name);
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 );
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));
#if 0 //C version
CvMat src = frame;
CvMat dst = lin_polar_img;
CvMat inverse = recovered_lin_polar_img;
cvLinearPolar(&src, &dst, center, maxRadius, flags);
cvLinearPolar(&dst, &inverse, center, maxRadius,flags + WARP_INVERSE_MAP);
#endif
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;
}