rotate.c

Go to the documentation of this file.

#include <math.h>

# define RpD ((2 * M_PI) / 360.)        /* radians/degree */
# define D2R(d) (double)(d * RpD)       /* degrees->radians */
# define R2D(d) (double)(d / RpD)       /* radians->degrees */



void G_rotate_around_point(double X0, double Y0, double *X1, double *Y1,
                           double angle)
{
    double dx = *X1 - X0;
    double dy = *Y1 - Y0;
    double c = cos(D2R(angle));
    double s = sin(D2R(angle));
    double dx1 = dx * c - dy * s;
    double dy1 = dx * s + dy * c;

    *X1 = X0 + dx1;
    *Y1 = Y0 + dy1;
}

void G_rotate_around_point_int(int X0, int Y0, int *X1, int *Y1, double angle)
{
    double x = (double)*X1;
    double y = (double)*Y1;

    if (angle == 0.0)
        return;

    G_rotate_around_point((double)X0, (double)Y0, &x, &y, angle);

    *X1 = (int)floor(x + 0.5);
    *Y1 = (int)floor(y + 0.5);
}