counter = 1
def generate_trail(df):
    global counter
    court = plt.imread("fullcourt.png")
    fig, ax = plt.subplots(figsize=(15, 11.5))
    plt.imshow(court, zorder=0, extent=[-47,47,-25,25])
    ax.set_xlim([-47, 0])
    ax.set_ylim([-25, 25])
    scat1 = ax.scatter([], [], color="red", alpha=0.4)
    first_frame = df.iloc[0]
    attacking = first_frame['Possession']
    is_home_team_attacking = is_home_team(attacking, Game_id)

    def sub_animate(j, frame, total_frames):
        x1, y1 = tuple(zip(*[list(pair.values())[0] for pair in j[is_home_team_attacking]]))
        if x1[0] > 0:
            x1 = [-x for x in x1]
        ax.scatter(x1, y1, color="red", alpha= frame * 0.75 / (total_frames), marker="o")


    for i in range(0, len(df)):
        sub_animate(df.iloc[i], i, len(df))
    ax.axis('off')
    fig.savefig(str(counter) + "_trail.png", dpi=300)
    counter += 1