问题描述
我正在寻找一种方法，可以让一个画布显示另一个画布的内容，而无需复制其中绘制的对象.第二个画布需要只是一个显示，它将在第一个画布上绘制的内容作为输入.
I'm looking for a way to make one canvas display the contents of another WITHOUT duplicating the objects that are drawn in it. The second canvas needs to be just a display which takes as input what is drawn on the first one.
我知道 .postscript 方法将内容写入文件或变量中，但我不知道如何(如果可能)让另一个画布将其显示为图像.
I know that the .postscript method writes the contents in a file or a variable, but I don't know how(if it's possible) to make another canvas display it as an image.
我忘了说，我的操作系统是 windows.如果有人也能告诉我一个跨平台的解决方案，那就太好了.
I forgot to mention, my operating system is windows. It would be great if someone can tell me a cross-platform solution also.
Edit2:我不想通过复制对象来做到这一点的原因是因为它们正在移动，并且每隔一段时间它们中的一些会被破坏并创建新的对象.此外，它是一个实时系统，复制对象及其行为可能会减慢速度.
the reason I don't want to do it by duplicating the objects is because they are moving and at some interval some of them are destroyed and new ones are created. Also it's a real-time system and duplicating the objects with their behaviors might slow things down.
推荐答案
没有内置的方法可以做到这一点.画布不支持任何类型的对等互连或复制.但是，如果您没有任何嵌入的小部件，将所有对象的副本保存在第二个画布中非常容易和快速.
There is no built-in way to do this. The canvas doesn't support any sort of peering or duplication. However, keeping copies of all the objects in a second canvas is pretty easy and fast if you don't have any embedded widgets.
一个简单的方法是将画布小部件子类化，然后创建 draw_line、draw_oval、coords 等的新实现以在对等画布上绘制.以下示例显示了如何以这种方式协调三个画布，其中 1000 个对象以不同的速率向下移动:
A simple way to do this is to subclass the canvas widget, then create new implementations of draw_line, draw_oval, coords, etc to draw on a peer canvas. The following example shows how to coordinate three canvases in this manner, with 1000 objects that are moving downward at different rates:
import Tkinter as tk
import random
class SampleApp(tk.Tk):
def __init__(self, *args, **kwargs):
tk.Tk.__init__(self, *args, **kwargs)
self.canvas1 = PeeredCanvas(self, width=300, height=300, border=1, relief="sunken")
self.canvas2 = PeeredCanvas(self, width=300, height=300, border=1, relief="sunken")
self.canvas3 = PeeredCanvas(self, width=300, height=300, border=1, relief="sunken")
self.canvas1.add_peer(self.canvas2)
self.canvas1.add_peer(self.canvas3)
toolbar = tk.Frame(self)
clear_button = tk.Button(self, text="Refresh", command=self.refresh)
clear_button.pack(in_=toolbar, side="left")
toolbar.pack(side="top", fill="x")
self.canvas1.pack(side="left", fill="both", expand=True)
self.canvas2.pack(side="left", fill="both", expand=True)
self.canvas3.pack(side="left", fill="both", expand=True)
self.animate(10)
def animate(self, delay):
'''Move all items down at a random rate'''
for item in self.canvas1.find_all():
delta_x = 0
delta_y = random.randrange(1, 4)
self.canvas1.move(item, delta_x, delta_y)
self.after(delay, self.animate, delay)
def refresh(self, count=100):
'''Redraw 'count' random circles'''
self.canvas1.delete("all")
width=self.canvas1.winfo_width()
height=self.canvas1.winfo_height()
for i in range(count):
if i%2 == 0:
tags = ("even",)
else:
tags = ("odd",)
x = random.randrange(10, width-10)
y = random.randrange(10, height-10)
radius = random.randrange(10,100, 10)/2
self.canvas1.create_oval([x,y, x+radius, y+radius], tags=tags)
self.canvas1.itemconfigure("even", fill="red", outline="white")
self.canvas1.itemconfigure("odd", fill="white", outline="red")
class PeeredCanvas(tk.Canvas):
'''A class that duplicates all objects on one or more peer canvases'''
def __init__(self, *args, **kwargs):
self.peers = []
tk.Canvas.__init__(self, *args, **kwargs)
def add_peer(self, peer):
if self.peers is None:
self.peers = []
self.peers.append(peer)
def move(self, *args, **kwargs):
tk.Canvas.move(self, *args, **kwargs)
for peer in self.peers:
peer.move(*args, **kwargs)
def itemconfigure(self, *args, **kwargs):
tk.Canvas.itemconfigure(self, *args, **kwargs)
for peer in self.peers:
peer.itemconfigure(*args, **kwargs)
def delete(self, *args, **kwargs):
tk.Canvas.delete(self, *args)
for peer in self.peers:
peer.delete(*args)
def create_oval(self, *args, **kwargs):
tk.Canvas.create_oval(self, *args, **kwargs)
for peer in self.peers:
peer.create_oval(*args, **kwargs)
app = SampleApp()
app.mainloop()
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