每当我运行代码时，窗口打开正常，但背景图像不会加载。虽然图像不会立即加载，但如果我最小化窗口并再次打开它，图像加载正常。
这是我的代码：

import pygame
import os
pygame.init()

WIDTH, HEIGHT = 500, 365

WIN = pygame.display.set_mode((WIDTH, HEIGHT))

BG = pygame.transform.scale(pygame.image.load(os.path.join("GameMap3.png")).convert_alpha(), (WIDTH, HEIGHT))
PLAYER1 = pygame.image.load(os.path.join("PlayerType1.gif"))

fps = 60
main_font = pygame.font.SysFont("comicsans", 50)
player_vel = 5
clock = pygame.time.Clock()

def Main():
    global BG

    while True:

        WIN.blit(BG, (0,0))

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                exit(0)

Main()