def build_C_paddle(self):
        """ Return coordinates of fiducial points in I_r; C """
        F = self.F
        ctrl_pts_x = torch.linspace(-1.0, 1.0, int(F / 2), dtype=torch.float64)
        ctrl_pts_y_top = -1 * torch.ones([int(F / 2)], dtype=torch.float64)
        ctrl_pts_y_bottom = torch.ones([int(F / 2)], dtype=torch.float64)
        ctrl_pts_top = torch.stack([ctrl_pts_x, ctrl_pts_y_top], dim=1)
        ctrl_pts_bottom = torch.stack([ctrl_pts_x, ctrl_pts_y_bottom], dim=1)
        C = torch.cat([ctrl_pts_top, ctrl_pts_bottom], dim=0)
        return C  # F x 2
 Return coordinates of fiducial points in I_r; C 
pytorchocr/modeling/transforms/tps.py