Pygame：帧重影？

Question

我正在使用pygame在python中处理动画环境。用户绘制每个帧，然后使用ffmpeg将动画保存为.avi影片。我想实现一个功能，但我不确定如何..帧重影。就像在绘制当前帧时显示前一帧一样。

我尝试创建一个名为ghost的表面，在按下下一帧键时复制当前帧。然后使用alpha级别10绘制它，但这没有正常工作。

我不知道该怎么做，这是任何认为他们有想法的人的源代码：

#Anim8

import pygame,subprocess,shutil
from os import makedirs
from pygame.locals import *
from random import randrange
pygame.init()
screen=pygame.display.set_mode((740,580))
draw=pygame.Surface((740,540))
draw.fill((200,200,200))
bcol=(200,200,200)
gui=pygame.Surface((740,40))
gui.fill((50,50,50))
size=2
color=(0,0,0)
screen.fill((200,200,200))
prevcol=0
newcol=0
f=0
msg=''
framerate=60
try:
    makedirs('anim')
except:
    pass
def DrawColors(x,y):
    pygame.draw.rect(gui, (255,0,0), (x+3,y+3,15,15),0)
    pygame.draw.rect(gui, (0,0,0), (x+3,y+21,15,15),0)
    pygame.draw.rect(gui, (0,255,0), (x+21,y+3,15,15),0)
    pygame.draw.rect(gui, (200,200,200), (x+21,y+21,15,15),0)
    pygame.draw.rect(gui, (0,0,255), (x+39,y+3,15,15),0)
while True:
    pygame.display.set_caption('Anim8 - Sam Tubb - '+'Frame: '+str(f)+' '+str(msg))
    mse=pygame.mouse.get_pos()
    screen.blit(gui, (0,0))
    DrawColors(0,0)
    screen.blit(draw,(0,40))
    key=pygame.key.get_pressed()
    if key[K_1]:
        framerate=10
        msg='Frame Rate set to 10'
    if key[K_2]:
        framerate=20
        msg='Frame Rate set to 20'
    if key[K_3]:
        framerate=30
        msg='Frame Rate set to 30'
    if key[K_4]:
        framerate=40
        msg='Frame Rate set to 40'
    if key[K_5]:
        framerate=50
        msg='Frame Rate set to 50'
    if key[K_6]:
        framerate=60
        msg='Frame Rate set to 60'
    if key[K_7]:
        framerate=70
        msg='Frame Rate set to 70'
    if key[K_8]:
        framerate=80
        msg='Frame Rate set to 80'
    if key[K_9]:
        framerate=90
        msg='Frame Rate set to 90'
    if key[K_0]:
        framerate=100
        msg='Frame Rate set to 100'

    if key[K_a]:
        pygame.image.save(draw, 'anim/frame'+str(f)+'.png')
        f+=1
    for e in pygame.event.get():
        if e.type==QUIT:
            shutil.rmtree('anim')
            exit()
        if e.type==KEYDOWN:
            if e.key==K_s:
                msg='Added Frame!'
                pygame.image.save(draw, 'anim/frame'+str(f)+'.png')
                f+=1
            if e.key==K_c:
                draw.fill(bcol)
            if e.key==K_r:
                name='anim'+str(randrange(0,999))+str(randrange(0,999))+'.avi'
                msg='Rendering: '+name
                pygame.display.set_caption('Anim8 - Sam Tubb - '+'Frame: '+str(f)+' '+str(msg))
                subprocess.call('ffmpeg -f image2 -s 640x480 -i anim/frame%01d.png -r '+str(framerate)+' '+name,shell=True)
                msg='Done!'
            if e.key==K_p:
                subprocess.call('ffplay '+name,shell=True)
        if e.type==MOUSEBUTTONDOWN:
            if e.button==1:
                try:
                    prevcol=color
                    newcol=gui.get_at(mse)
                    if newcol==(50,50,50):
                        newcol=prevcol
                    color=newcol
                except:
                    pass
            if e.button==3:
                try:
                    prevcol=bcol
                    newcol=gui.get_at(mse)
                    if newcol==(50,50,50):
                        newcol=prevcol
                    draw.fill(newcol)
                    bcol=newcol
                except:
                    pass
            if e.button==4:
                size+=1
                if size>7:
                    size=7
            if e.button==5:
                size-=1
                if size==0:
                    size=1 
        if e.type == pygame.MOUSEMOTION:
            lineEnd = pygame.mouse.get_pos()
            lineEnd = (lineEnd[0],lineEnd[1]-40)
            if pygame.mouse.get_pressed() == (1, 0, 0):
                    pygame.draw.line(draw, color, lineStart, lineEnd, size)
            lineStart = lineEnd

    pygame.display.flip()

哦，另一方面，如果有人好奇，这就是输出的样子......我做了一个新的一年的动画：