Python 当我用键绑定更改 self.surf 时，如何阻止我的角色缩小

我正在试着让游戏中的玩家/精灵从按键"左"和"右"切换.然而，当我这样做的时候，精灵缩小了(保留了它的Hitbox)，有人能帮忙吗？

class Player(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__() 
        img_player = pygame.image.load("../graphics/left_player.png")
        self.image = pygame.transform.scale(img_player,(50, 50))
        self.surf = self.image
        self.rect = self.surf.get_rect()
   
        self.pos = vec((10, 360))
        self.vel = vec(0,0)
        self.acc = vec(0,0)
        self.jumping = False
        self.score = 10
 
    def move(self):
        self.acc = vec(0,0.5)
    
        pressed_keys = pygame.key.get_pressed()
                
        if pressed_keys[K_LEFT]:
            self.acc.x = -ACC
        if pressed_keys[K_RIGHT]:
            self.acc.x = ACC
                 
        self.acc.x += self.vel.x * FRIC
        self.vel += self.acc
        self.pos += self.vel + 0.5 * self.acc
         
        if self.pos.x > WIDTH:
            self.pos.x = 0
        if self.pos.x < 0:
            self.pos.x = WIDTH
             
        self.rect.midbottom = self.pos
 
    def jump(self): 
        hits = pygame.sprite.spritecollide(self, platforms, False)
        if hits and not self.jumping:
           self.jumping = True
           self.vel.y = -15 + game_upgrade_jump
           pygame.mixer.Sound.play(jump_sound)
 
    def cancel_jump(self):
        if self.jumping:
            if self.vel.y < -3:
                self.vel.y = -3
 
    def update(self):
        hits = pygame.sprite.spritecollide(self ,platforms, False)
        if self.vel.y > 0:        
            if hits:
                if self.pos.y < hits[0].rect.bottom:
                    if hits[0].point == True:   
                        hits[0].point = False   
                        self.score += (1 + game_upgrade_points)     
                        print('score changed: ', self.score)
                    self.pos.y = hits[0].rect.top +1
                    self.vel.y = 0
                    self.jumping = False