由于动态更新的性能问题,我需要在画布上直接绘制很多矩形作为非常低的级别,也就是说不使用matplotlib.patches,因为我们必须使用经典的GUI.

更准确地说,我想只绘制一个矩形,而不仅仅是所有的图形.

可能吗 ？

这是我使用Joe Kington给出的链接的测试代码.

#!/usr/bin/env python3

from random import randint, choice

import time

import matplotlib.pyplot as plt

import matplotlib.patches as mpatches

import matplotlib.colors as colors

import matplotlib

back_color = "black"

colors = ['red', 'green', 'cyan', 'yellow']

width = 16

height = 16

ax = plt.subplot(111)

canvas = ax.figure.canvas

ax.set_xlim([0, width])

ax.set_ylim([0, height])

def update():

global ax, canvas, colors, width, height

x = randint(0, width - 1)

y = randint(0, height - 1)

rect = mpatches.Rectangle(

(x, y), 1, 1,

facecolor = choice(colors),

edgecolor = back_color

)

start = time.time()

ax.draw_artist(rect)

canvas.blit(ax.bbox)

print("draw >>>", time.time() - start)

timer = canvas.new_timer(interval = 1)

timer.add_callback(update)

timer.start()

plt.show()

在Mac O $下,我获得以下消息.

Traceback (most recent call last):

File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/matplotlib/backend_bases.py", line 1203, in _on_timer

ret = func(*args, **kwargs)

File "/Users/xxx/test.py", line 86, in update

ax.draw_artist(rect)

File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/matplotlib/axes.py", line 2100, in draw_artist

a.draw(self._cachedRenderer)

File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/matplotlib/artist.py", line 56, in draw_wrapper

draw(artist, renderer, *args, **kwargs)

File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/matplotlib/patches.py", line 393, in draw

gc = renderer.new_gc()

File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/site-packages/matplotlib/backends/backend_macosx.py", line 97, in new_gc

self.gc.save()

RuntimeError: CGContextRef is NULL

对于Maverick用户

对于想要使用以下代码以及动画的Mac用户,我有一个好消息.我在没有任何软件的Mac上重新安装了Maverick OS,这称为干净安装,然后我安装了Anaconda和XQuark(see this).

要使动画有效,只需在任何其他matplotlib导入之前使用以下两行.

import matplotlib

matplotlib.use('TkAgg')

我认为这适用于Anaconda支持的任何Mac OS.只有Maverick才需要使用XQuark.

解决方法:

您当前的代码有两个问题.

>你没有先画出画布而试图搞砸.你得到的错误是后端特定的,但基本上,它说的是画布的渲染器还没有被初始化.

>您没有将矩形艺术家添加到轴.因此,调用ax.draw_artist(rect)时不会被绘制.

这是一个有效的例子：

from random import randint, choice

import time

import matplotlib.pyplot as plt

import matplotlib.patches as mpatches

back_color = "black"

colors = ['red', 'green', 'cyan', 'yellow']

width, height = 16, 16

fig, ax = plt.subplots()

ax.set(xlim=[0, width], ylim=[0, height]) # Or use "ax.axis([x0,x1,y0,y1])"

# Be sure to draw the canvas once before we start blitting. Otherwise

# a) the renderer doesn't exist yet, and b) there's noting to blit onto

fig.canvas.draw()

def update():

x = randint(0, width - 1)

y = randint(0, height - 1)

rect = mpatches.Rectangle(

(x, y), 1, 1,

facecolor = choice(colors),

edgecolor = back_color

)

ax.add_artist(rect)

start = time.time()

ax.draw_artist(rect)

fig.canvas.blit(ax.bbox)

print("draw >>>", time.time() - start)

timer = fig.canvas.new_timer(interval=1)

timer.add_callback(update)

timer.start()

plt.show()

但是,在这一点上,每次添加新艺术家都会更有意义.相反,添加初始矩形并每次更新它.例如：

from random import randint, choice

import time

import matplotlib.pyplot as plt

import matplotlib.patches as mpatches

back_color = "black"

colors = ['red', 'green', 'cyan', 'yellow']

width, height = 16, 16

fig, ax = plt.subplots()

ax.set(xlim=[0, width], ylim=[0, height]) # Or use "ax.axis([x0,x1,y0,y1])"

rect = mpatches.Rectangle(

(0, 0), 1, 1,

facecolor = choice(colors),

edgecolor = back_color

)

ax.add_artist(rect)

# Be sure to draw the canvas once before we start blitting. Otherwise

# a) the renderer doesn't exist yet, and b) there's noting to blit onto

fig.canvas.draw()

def update():

x = randint(0, width - 1)

y = randint(0, height - 1)

rect.set(xy=[x,y], facecolor=choice(colors))

start = time.time()

ax.draw_artist(rect)

fig.canvas.blit(ax.bbox)

print("draw >>>", time.time() - start)

timer = fig.canvas.new_timer(interval=1)

timer.add_callback(update)

timer.start()

plt.show()

标签：python,matplotlib

来源： https://codeday.me/bug/20190708/1405723.html