How to fix "Type Error : Invalid Dimensions for image data" error when I view an image using matplotlib

Question

I'm trying to convert an image to grayscale and show it using pyplot. The steps I am taking are:

Step 1: Reading an image as input using Pillow in python

Step 2: Converting it into grayscale image using .convert('LA')

This is the code:

import numpy as np
from PIL import Image
import matplotlib.pyplot as plt

img = Image.open('28.jpg').convert('LA')
img.save('greyscale.png')

img=np.array(img)
print (img.shape)
plt.imshow(img)

Which outputs this as the shape of the np.array:

(360, 480, 2)

The problem is when I try to view the output of this grayscale image using matplotlib.pyplot it throws the following error error:

TypeError                                 Traceback (most recent call last)
<ipython-input-4-f6fac0acd82f> in <module>
      1 img = np.array(img)
      2 print (img.shape)
----> 3 plt.imshow(img)

~/.local/lib/python3.6/site-packages/matplotlib/pyplot.py in imshow(X, cmap, norm, aspect, interpolation, alpha, vmin, vmax, origin, extent, shape, filternorm, filterrad, imlim, resample, url, data, **kwargs)
   2697         filternorm=filternorm, filterrad=filterrad, imlim=imlim,
   2698         resample=resample, url=url, **({"data": data} if data is not
-> 2699         None else {}), **kwargs)
   2700     sci(__ret)
   2701     return __ret

~/.local/lib/python3.6/site-packages/matplotlib/__init__.py in inner(ax, data, *args, **kwargs)
   1808                         "the Matplotlib list!)" % (label_namer, func.__name__),
   1809                         RuntimeWarning, stacklevel=2)
-> 1810             return func(ax, *args, **kwargs)
   1811 
   1812         inner.__doc__ = _add_data_doc(inner.__doc__,

~/.local/lib/python3.6/site-packages/matplotlib/axes/_axes.py in imshow(self, X, cmap, norm, aspect, interpolation, alpha, vmin, vmax, origin, extent, shape, filternorm, filterrad, imlim, resample, url, **kwargs)
   5492                               resample=resample, **kwargs)
   5493 
-> 5494         im.set_data(X)
   5495         im.set_alpha(alpha)
   5496         if im.get_clip_path() is None:

~/.local/lib/python3.6/site-packages/matplotlib/image.py in set_data(self, A)
    636         if not (self._A.ndim == 2
    637                 or self._A.ndim == 3 and self._A.shape[-1] in [3, 4]):
--> 638             raise TypeError("Invalid dimensions for image data")
    639 
    640         if self._A.ndim == 3:

TypeError: Invalid dimensions for image data

This is the image I am trying to read and convert it into grayscale 28.jpg

Use `.convert('L')` as shown in the duplicate. (Because jpg images don't have an alpha channel anyways) — ImportanceOfBeingErnest, Jun 11 '19 at 14:28

score 0 · Answer 1 · answered Jun 11 '19 at 06:23

0

You don't have to save the image as an np.array, just give the converted image to plt.imshow() directly. Like this:

import numpy as np
from PIL import Image
import matplotlib.pyplot as plt

img = Image.open('28.jpg').convert('LA')
img.save('greyscale.png')

plt.imshow(img)

You can still store the image as an np.array is you want to, just make sure to give it a different name.

Also, if you want to show the image, don't forget to put plt.show() at the end.

answered Jun 11 '19 at 06:23

funie200

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I am still getting the same error message – Sanjay Moharana Jun 11 '19 at 06:27
@SanjayMoharana Try it in fresh, it works. – Amazing Things Around You Jun 11 '19 at 06:28
@AmazingThingsAroundYou Its not working.Its still throwing same error message. – Sanjay Moharana Jun 11 '19 at 06:37
@SanjayMoharana Can you post the full error traceback in your question? – funie200 Jun 11 '19 at 06:41
@SanjayMoharana Looking at the error traceback, you did not try my answer because you're still storing the image as an `np.array`. – funie200 Jun 11 '19 at 06:50
@funie200 The error still persists even after not storing the image as numpy array and adding plt.show() at the end.I just executed your solution including plt.show() at end in a fresh ipython notebook but still i am getting this error. – Sanjay Moharana Jun 11 '19 at 06:58
@SanjayMoharana Are you even listening my friend, what funie200 said? You are not trying the answer. Do not convert to Numpy array please. – Amazing Things Around You Jun 11 '19 at 07:33
@SanjayMoharana Works fine for me, what is the image that you are trying to show? – funie200 Jun 11 '19 at 08:34
@AmazingThingsAroundYou You are not getting me...I have exactly tried his solution **without converting the image into numpy array** and just simply tried to output the grayscale image. I am still getting the same error even after executing the same code – Sanjay Moharana Jun 11 '19 at 08:39
@funie200 I am trying to show the grayscale image – Sanjay Moharana Jun 11 '19 at 08:41
@SanjayMoharana Yes I know, but can you upload the image to SO, so I can test it with the exact image you are using. The `28.jpg` image. – funie200 Jun 11 '19 at 08:42
@SanjayMoharana Tell us something about the image you have. – Amazing Things Around You Jun 11 '19 at 10:07
@AmazingThingsAroundYou The image link is given above. And what I am trying is to convert 28.jpg into grayscale image and save it in the respective directory.Meanwhile the grayscale image is getting saved but when I am trying to visualise this image as output then I am seeing this error. – Sanjay Moharana Jun 11 '19 at 11:30

How to fix "Type Error : Invalid Dimensions for image data" error when I view an image using matplotlib

1 Answers1