def annulus_1_to_0_based(annulus):
    """
    Convert annulus parameters from 1- to 0-based indexing

    Input:
        annulus: (list of) length-6-tuple(s) with parameters to generate annulus:
            coord_center_x: x-coordinate of center (pixels; 1-based)
            coord_center_y: y-coordinate of center (pixels; 1-based)
            inner_radius: inner radius (pixels)
            outer_radius: outer_radius (pixels)
            start_angle: start angle of annulus sector (deg; 0 deg to the right and positive rotation counterclockwise)
            end_angle: end angle of annulus sector (deg; 0 deg to the right and positive rotation counterclockwise)

    Output:
        annulus: same as for input, but with coord_center_x and coord_center_y
            0-based

    File written by Rob van Holstein
    Function status: verified
    """
    if type(annulus) is tuple:
        annulus = (annulus[0] - 1,) + (annulus[1] - 1,) + annulus[2:]
    elif type(annulus) is list:
        for i, x in enumerate(annulus):
            x = (x[0] - 1,) + (x[1] - 1,) + x[2:]
            annulus[i] = x
    return annulus
