在pyglet中将背景图像另存为透明

Question

在我的简单pyglet应用程序中执行一些操作后，我想将场景录制成png图像 这包括透明度。 我设置了pyglet.gl.glClearColor(0,0,0,0)，试图使背景透明。场景仅由精灵对象和背景组成。要记录当前图像，我使用以下代码段

pyglet.image.get_buffer_manager().get_color_buffer().save(filename)

但是，这种方法的问题是alpha通道没有存储在png中。有没有办法在没有背景的情况下拍摄图像？如果是这样的话，我能用透明通道在png中分别捕捉每个精灵吗

尝试一个最小的可复制示例：

import pymunk.pygame_util
import pymunk
from pymunk import Vec2d, BB
import pymunk.pygame_util
import pymunk.autogeometry
import numpy as np
import pyglet
import math
import random
import pymunk.pyglet_util
from pyglet.gl import *
HOME_DIR = "this is the home directory path"
class myPygletGame(pyglet.window.Window):
    draw_options = pymunk.pyglet_util.DrawOptions()
    pyglet.gl.glClearColor(0,0,0,0)
    width = 1000
    height = 1000
    space = pymunk.Space()
    space.gravity = 0, -600
    batch = pyglet.graphics.Batch()
    def __init__(self):
        super(myPygletGame, self).__init__()
        self.set_size(self.width, self.height)
        pyglet.clock.schedule_interval(self.update, 1/60)
        pyglet.clock.schedule_once(self.spawn_logo1, 1)
        pyglet.app.run()
    def on_draw(self,):
        pyglet.gl.glClearColor(0,0,0,0)
        self.clear()
        self.render()
        self.batch.draw()
    def render(self):
        glClearColor(  0, 0,   0, 0)  # background color
        glEnable(GL_LINE_SMOOTH)
        glEnable(GL_BLEND)                                  # transparency
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)   # transparency
    def update(self,dt):
        dt = 1.0/60. #override dt to keep physics simulation stable
        self.space.step(dt)
    def spawn_logo1(self,dt):
        pyglet.gl.glClearColor(0,0,0,0)
        self.Mycar = Car(self)
        self.save_a_frame()
    def save_a_frame(self):
        filename=" frame-sec.png"
        pyglet.image.get_buffer_manager().get_color_buffer().save(HOME_DIR + filename)

class Car():
    def __init__(self, WindowGameRef):
        self.WindowGameRef = WindowGameRef
        self.imagePath = "imageSprite.png"
        b = pymunk.Body(mass=1, moment=10000)
        shape = pymunk.Segment(b,  [100,100],  [200,200], 2)
        WindowGameRef.space.add(shape , b) 
        pyglet.resource.path = [HOME_DIR]
        pyglet.resource.reindex()
        self.logo_img = pyglet.resource.image(self.imagePath)
        self.sprite = pyglet.sprite.Sprite(self.logo_img, batch=self.WindowGameRef.batch)
        self.sprite.position = b.position

if __name__ == "__main__":
    mygame = myPygletGame()