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Matplotlib（pyplot）savefig输出空白图像

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问题：Matplotlib（pyplot）savefig输出空白图像
回答 0
回答 1
回答 2
回答 3
回答 4

问题：Matplotlib（pyplot）savefig输出空白图像

我正在尝试保存使用matplotlib创建的图；但是，图像保存为空白。

这是我的代码：

plt.subplot(121)
plt.imshow(dataStack, cmap=mpl.cm.bone)

plt.subplot(122)
y = copy.deepcopy(tumorStack)
y = np.ma.masked_where(y == 0, y)

plt.imshow(dataStack, cmap=mpl.cm.bone)
plt.imshow(y, cmap=mpl.cm.jet_r, interpolation='nearest')

if T0 is not None:
    plt.subplot(123)
    plt.imshow(T0, cmap=mpl.cm.bone)

    #plt.subplot(124)
    #Autozoom

#else:
    #plt.subplot(124)
    #Autozoom

plt.show()
plt.draw()
plt.savefig('tessstttyyy.png', dpi=100)

tessstttyyy.png为空白（也尝试使用.jpg）

点击查看英文原文

I am trying to save plots I make using matplotlib; however, the images are saving blank.

Here is my code:

plt.subplot(121)
plt.imshow(dataStack, cmap=mpl.cm.bone)

plt.subplot(122)
y = copy.deepcopy(tumorStack)
y = np.ma.masked_where(y == 0, y)

plt.imshow(dataStack, cmap=mpl.cm.bone)
plt.imshow(y, cmap=mpl.cm.jet_r, interpolation='nearest')

if T0 is not None:
    plt.subplot(123)
    plt.imshow(T0, cmap=mpl.cm.bone)

    #plt.subplot(124)
    #Autozoom

#else:
    #plt.subplot(124)
    #Autozoom

plt.show()
plt.draw()
plt.savefig('tessstttyyy.png', dpi=100)

And tessstttyyy.png is blank (also tried with .jpg)

回答 0

首先，什么时候会发生T0 is not None？我会测试一下，然后再调整传递给的值plt.subplot()；可以尝试使用值131、132和133，或者取决于是否T0存在的值。

其次，在plt.show()调用之后，创建一个新图形。为了解决这个问题，您可以

  1. 调用plt.savefig('tessstttyyy.png', dpi=100)之前调用plt.show()

  2. show()通过调用plt.gcf()“获取当前图形”来保存图形，然后可以随时调用savefig()此Figure对象。

例如： 

fig1 = plt.gcf()
plt.show()
plt.draw()
fig1.savefig('tessstttyyy.png', dpi=100)

在您的代码中，“ tesssttyyy.png”为空白，因为它保存的是新图形，该图形上没有任何内容。

点击查看英文原文

First, what happens when T0 is not None? I would test that, then I would adjust the values I pass to plt.subplot(); maybe try values 131, 132, and 133, or values that depend whether or not T0 exists.

Second, after plt.show() is called, a new figure is created. To deal with this, you can

  1. Call plt.savefig('tessstttyyy.png', dpi=100) before you call plt.show()

  2. Save the figure before you show() by calling plt.gcf() for “get current figure”, then you can call savefig() on this Figure object at any time.

For example: 

fig1 = plt.gcf()
plt.show()
plt.draw()
fig1.savefig('tessstttyyy.png', dpi=100)

In your code, ‘tesssttyyy.png’ is blank because it is saving the new figure, to which nothing has been plotted.

回答 1

plt.show() 应该来 plt.savefig()

说明：plt.show()清除所有内容，因此以后任何事情都会在一个新的空白图形上发生

点击查看英文原文

plt.show() should come after plt.savefig()

Explanation: plt.show() clears the whole thing, so anything afterwards will happen on a new empty figure

回答 2

更改功能的顺序为我解决了问题：

  • 首先 保存情节
  • 然后 显示剧情

如下：

plt.savefig('heatmap.png')

plt.show()
点击查看英文原文

change the order of the functions fixed the problem for me:

  • first Save the plot
  • then Show the plot

as following:

plt.savefig('heatmap.png')

plt.show()

回答 3

在show（）对我有用之前调用savefig。

fig ,ax = plt.subplots(figsize = (4,4))
sns.barplot(x='sex', y='tip', color='g', ax=ax,data=tips)
sns.barplot(x='sex', y='tip', color='b', ax=ax,data=tips)
ax.legend(['Male','Female'], facecolor='w')

plt.savefig('figure.png')
plt.show()
点击查看英文原文

Calling savefig before show() worked for me.

fig ,ax = plt.subplots(figsize = (4,4))
sns.barplot(x='sex', y='tip', color='g', ax=ax,data=tips)
sns.barplot(x='sex', y='tip', color='b', ax=ax,data=tips)
ax.legend(['Male','Female'], facecolor='w')

plt.savefig('figure.png')
plt.show()

回答 4

让我给一个更详细的例子：

import numpy as np
import matplotlib.pyplot as plt


def draw_result(lst_iter, lst_loss, lst_acc, title):
    plt.plot(lst_iter, lst_loss, '-b', label='loss')
    plt.plot(lst_iter, lst_acc, '-r', label='accuracy')

    plt.xlabel("n iteration")
    plt.legend(loc='upper left')
    plt.title(title)
    plt.savefig(title+".png")  # should before plt.show method

    plt.show()


def test_draw():
    lst_iter = range(100)
    lst_loss = [0.01 * i + 0.01 * i ** 2 for i in xrange(100)]
    # lst_loss = np.random.randn(1, 100).reshape((100, ))
    lst_acc = [0.01 * i - 0.01 * i ** 2 for i in xrange(100)]
    # lst_acc = np.random.randn(1, 100).reshape((100, ))
    draw_result(lst_iter, lst_loss, lst_acc, "sgd_method")


if __name__ == '__main__':
    test_draw()

点击查看英文原文

let’s me give a more detail example:

import numpy as np
import matplotlib.pyplot as plt


def draw_result(lst_iter, lst_loss, lst_acc, title):
    plt.plot(lst_iter, lst_loss, '-b', label='loss')
    plt.plot(lst_iter, lst_acc, '-r', label='accuracy')

    plt.xlabel("n iteration")
    plt.legend(loc='upper left')
    plt.title(title)
    plt.savefig(title+".png")  # should before plt.show method

    plt.show()


def test_draw():
    lst_iter = range(100)
    lst_loss = [0.01 * i + 0.01 * i ** 2 for i in xrange(100)]
    # lst_loss = np.random.randn(1, 100).reshape((100, ))
    lst_acc = [0.01 * i - 0.01 * i ** 2 for i in xrange(100)]
    # lst_acc = np.random.randn(1, 100).reshape((100, ))
    draw_result(lst_iter, lst_loss, lst_acc, "sgd_method")


if __name__ == '__main__':
    test_draw()