M_2__PI            96 modules/imgproc/src/lsd.cpp     while(diff <= -CV_PI) diff += M_2__PI;
M_2__PI            97 modules/imgproc/src/lsd.cpp     while(diff >   CV_PI) diff -= M_2__PI;
M_2__PI          1147 modules/imgproc/src/lsd.cpp         n_theta -= M_2__PI;