我在使用 im.show() 时遇到错误

Question

我正在尝试保存灰度图像（256,256,1）并在输出中显示它。

im = data.astype(np.uint8)
print im.shape
im = np.transpose(im, (2,1,0)) 
print im.shape
im.show()

但是，我收到以下错误：

(256, 256, 1)
Traceback (most recent call last):
  File "lmdb_reader.py", line 37, in <module>
    plt.imshow(im)
  File "/home/se/anaconda2/envs/caffeenv/lib/python2.7/site-packages/matplotlib/pyplot.py", line 3029, in imshow
    **kwargs)
  File "/home/se/anaconda2/envs/caffeenv/lib/python2.7/site-packages/matplotlib/__init__.py", line 1819, in inner
    return func(ax, *args, **kwargs)
  File "/home/se/anaconda2/envs/caffeenv/lib/python2.7/site-packages/matplotlib/axes/_axes.py", line 4922, in imshow
    im.set_data(X)
  File "/home/se/anaconda2/envs/caffeenv/lib/python2.7/site-packages/matplotlib/image.py", line 453, in set_data
    raise TypeError("Invalid dimensions for image data")
TypeError: Invalid dimensions for image data

Answer 1

请注意，im.show()不存在，但这可能只是问题中的拼写错误。真正的问题如下：

Matplotlibpyplot.imshow可以绘制尺寸(N,M)（灰度）或(N,M,3)（RGB 颜色）的图像。你的形象是(N,M,1)；因此我们需要去掉最后一个维度。

import matplotlib.pyplot as plt
import numpy as np
#create data of shape (256,256,1)
data = np.random.rand(256,256,1)*255
im = data.astype(np.uint8)
print im.shape # prints (256L, 256L, 1L)
# (256,256,1) cannot be plotted, therefore 
# we need to get rid of the last dimension:
im = im[:,:,0]
print im.shape # (256L, 256L)
# now the image can be plotted
plt.imshow(im, cmap="gray")
plt.show()

Answer 2

您需要在调用 matplotlib.pyplot.show() 之前指定颜色图。默认情况下，当您传递 3D 数组时，该函数需要 RGB 图像。

例子：

im = np.squeeze(im)
plt.imshow(im,cmap='gray')
plt.show()