Adding/removing camera distortion

Gandalf also supplies some functions for adding and removing the image plane distortion from an image point. So for instance

      Gan_Camera CameraD;
      Gan_Vector3 v3x, v3xu;

      /* build camera with one parameter of radial distortion */
      gan_camera_build_radial_distortion_1 ( &CameraD,
                                       /*    ZH     FY     FX     Y0     X0 */
                                             100.0, 700.0, 500.0, 150.0, 100.0,
                                       /*    K1 */
                                             0.001 );

      /* build image point x assumed to have distortion */
      gan_vec3_fill_q ( &v3x, 50.0, -80.0, 100.0 );

      /* remove distortion from image point x --> xu */
      gan_camera_remove_distortion_q ( &CameraD, &v3x, &v3xu );

removes the distortion from the image point x, producing an undistorted point xu. Given the camera 3D point ${\bf X}$ that projects onto x, xu is defined as the point on the image onto which the equivalent linear camera (i.e. the linear camera with the same $f_x$, $f_y$, $x_0$, $y_0$ and $z_h$) would project when applied to ${\bf X}$. The in-place version of this function is

      /* remove distortion from image point x --> xu in-place */
      gan_camera_remove_distortion_i ( &CameraD, &v3x );

The reverse is to add distortion to an image point. Given a non-linear camera, this means converting a point projected with the equivalent linear camera to a point projected with the non-linear camera:

      /* build image point xu assumed to have NO distortion */
      gan_vec3_fill_q ( &v3xu, 50.0, -80.0, 100.0 );

      /* add distortion to image point xu --> x */
      gan_camera_add_distortion_q ( &CameraD, &v3xu, &v3x ); /* OR */
      gan_camera_add_distortion_i ( &CameraD, &v3xu ); /* in-place */

The single precision versions of these routines are

      Gan_Camera_f CameraF;
      Gan_Vector3_f v3x, v3xu;

      /* build camera with one parameter of radial distortion */
      gan_cameraf_build_radial_distortion_1 ( &CameraF,
                                        /*    ZH      FY      FX      Y0      X0 */
                                              100.0F, 700.0F, 500.0F, 150.0F, 100.0F,
                                        /*    K1 */
                                              0.001F );

      /* build image point x assumed to have distortion */
      gan_vec3f_fill_q ( &v3x, 50.0F, -80.0F, 100.0F );

      /* remove distortion from image point x --> xu */
      gan_cameraf_remove_distortion_q ( &CameraF, &v3x, &v3xu ); /* OR */
      gan_cameraf_remove_distortion_i ( &CameraF, &v3x ); /* in-place */

      /* build image point xu assumed to have NO distortion */
      gan_vec3f_fill_q ( &v3xu, 50.0F, -80.0F, 100.0F );

      /* add distortion to image point xu --> x */
      gan_cameraf_add_distortion_q ( &CameraF, &v3xu, &v3x ); /* OR */
      gan_cameraf_add_distortion_i ( &CameraF, &v3xu ); /* in-place */