def source_dx_dy(source_pos_x, source_pos_y, cog_x, cog_y):
    """
    Compute the coordinates of the vector (dx, dy) from the center of gravity to the source position

    Parameters
    ----------
    source_pos_x: X coordinate of the source in the camera
    source_pos_y: Y coordinate of the source in the camera
    cog_x: X coordinate of the center of gravity in the camera
    cog_y: Y coordinate of the center of gravity in the camera

    Returns
    -------
    (dx, dy)
    """
    return source_pos_x - cog_x, source_pos_y - cog_y