问题描述

我在 NetworkX 中有一个包含一些信息的图表.图表显示后，我想将其保存为 jpg 或 png 文件.我使用了 matplotlib 函数 savefig 但是当图像被保存时，它不包含任何东西.它只是一个白色的图像.

I have a graph in NetworkX containing some info. After the graph is shown, I want to save it as jpg or png file. I used the matplotlib function savefig but when the image is saved, it does not contain anything. It is just a white image.

这是我写的示例代码:

import networkx as nx
import matplotlib.pyplot as plt

fig = plt.figure(figsize=(12,12))
ax = plt.subplot(111)
ax.set_title('Graph - Shapes', fontsize=10)

G = nx.DiGraph()
G.add_node('shape1', level=1)
G.add_node('shape2', level=2)
G.add_node('shape3', level=2)
G.add_node('shape4', level=3)
G.add_edge('shape1', 'shape2')
G.add_edge('shape1', 'shape3')
G.add_edge('shape3', 'shape4')
pos = nx.spring_layout(G)
nx.draw(G, pos, node_size=1500, node_color='yellow', font_size=8, font_weight='bold')

plt.tight_layout()
plt.show()
plt.savefig("Graph.png", format="PNG")

为什么保存的图片里面没有任何东西(只有白色)?

Why is the image saved without anything inside (just white) ?

这是保存的图像(只是空白):

This is the image saved (just blank):

推荐答案

与plt.show方法有关.

show方法的帮助:

def show(*args, **kw):
    """
    Display a figure.

    When running in ipython with its pylab mode, display all
    figures and return to the ipython prompt.

    In non-interactive mode, display all figures and block until
    the figures have been closed; in interactive mode it has no
    effect unless figures were created prior to a change from
    non-interactive to interactive mode (not recommended).  In
    that case it displays the figures but does not block.

    A single experimental keyword argument, *block*, may be
    set to True or False to override the blocking behavior
    described above.
    """

当您在脚本中调用 plt.show() 时，似乎文件对象仍处于打开状态，而 plt.savefig 写入方法无法读取那个流完全.但是 plt.show 有一个 block 选项可以改变这种行为，所以你可以使用它:

When you call plt.show() in your script, it seems something like file object is still open, and plt.savefig method for writing can not read from that stream completely. but there is a block option for plt.show that can change this behavior, so you can use it:

plt.show(block=False)
plt.savefig("Graph.png", format="PNG")

或者只是评论它:

# plt.show()
plt.savefig("Graph.png", format="PNG")

或者在展示之前保存:

plt.savefig("Graph.png", format="PNG")
plt.show()

演示:这里

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