Правильная загрузка полупрозрачных спрайтов

class Spritesheet:
    def __init__(self, filename):
        self.spritesheet = pg.image.load(filename).convert_alpha()
 
    def get_image(self, x, y, width, height):
        image = pg.Surface((width, height))
        image.blit(self.spritesheet, (0, 0), (x, y, width, height))
        return image

class Fire(pg.sprite.Sprite):
    def __init__(self, game, x, y):
        self._layer = FIRE_LAYER
        self.groups = game.all_sprites, game.lights
        pg.sprite.Sprite.__init__(self, self.groups)
        self.game = game
        self.load_images()
        self.current_frame = 0
        self.last_update = 0
        self.image = self.fire_frames[0]
        self.rect = self.image.get_rect()
        self.rect.x = x
        self.rect.y = y
 
    def load_images(self):
        self.fire_frames = [self.game.spritesheet.get_image(0, 144, 48, 48),
                            self.game.spritesheet.get_image(48, 144, 48, 48),
                            self.game.spritesheet.get_image(96, 144, 48, 48),
                            self.game.spritesheet.get_image(144, 144, 48, 48)]
        for frame in self.fire_frames:
            frame.set_colorkey(BLACK)
 
    def update(self):
        self.animate()
 
    def animate(self):
        now = pg.time.get_ticks()
        if now - self.last_update > 120:
            self.last_update = now
            self.current_frame = (self.current_frame + 1) % len(self.fire_frames)
            self.image = self.fire_frames[self.current_frame]
            self.image = pg.transform.scale(self.image, (144, 144))

class Spritesheet:
    def __init__(self, filename):
        self.spritesheet = pg.image.load(filename)
        self.spritesheet = pg.Surface.convert_alpha(self.spritesheet)
 
    def get_image(self, x, y, width, height):
        image = pg.Surface((width, height), pg.SRCALPHA)
        image.blit(self.spritesheet, (0, 0), (x, y, width, height))
        return image