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I run this simple code in below to load images from a folder and after around 200 images I get this error "Fail to allocate bitmap". The problem mainly in the matplotlib.pyplot. I try to free the memory inside the loop using the 7 ways which shown in the code but unfortunately useless.

I found similar question but with no answer! I hope to receive solution for this problem.

from __future__ import division

import os
import numpy as np
import gc
from os import listdir
from os.path import isfile, join
import matplotlib.pyplot as plt
from PIL import Image


def test():
    
    entries = os.listdir(r"D:\Images")
    for entry in entries:
     if entry.endswith(".jpg"):
     
      img = np.array(Image.open(r"D:\Images\{}".format(entry)))
      fig, ax = plt.subplots(1)

      #Many ways I added to free the memory#
      plt.close('all')
      fig.clear()
      ax.clear()
      plt.clf()
      gc.collect()
      plt.close(fig)
      del img
      #####################################

UPDATE:

My Environment is Anaconda 3, OS: Windows 10

UPDATE:

I replaced this line:

fig, ax = plt.subplots(1)

With

fig, ax = plt.subplots(num=1, clear=True)

And the code became running for longer time, before I got the error after loading 185 images but now after I added "clear=true" the error appears after 369 images so this almost became the double. but the problem is still exist!

Waleed ELerksosy
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2 Answers2

2

I got this error while creating hundreds of plots and saving them to files. Calling the following line after each plot completely removed the above error for me:

plt.clf()

I can recommend this answer for more info.: https://stackoverflow.com/a/8228808/1935801

Morten Grum
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My guess is you never close the image file (https://pillow.readthedocs.io/en/stable/reference/Image.html). I don't even see that you plot anything this way?


with Image.open(r"D:\Images\{}".format(entry)) as im:
   img = np.array(im)

If you are still sure it is matplotlib, it would be good to see that actual error message and know what environment you are calling the above from.

Jody Klymak
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  • Yes, I'm sure the error "Fail to allocate bitmap" comes because of matplotlib, mainly in this line of code: "fig, ax = plt.subplots()". Can you please explain me, what do you mean with the actual error message? thank you! – Waleed ELerksosy May 02 '21 at 08:15
  • Error messages in python include a stack trace. You have also not indicated what environment you are running in. Unfortunately the rest of us cannot reproduce your problem. If it is really matplotlib causing the problem you should be able to reproduce without Pillow by plotting random arrays. – Jody Klymak May 02 '21 at 15:24
  • Just to be clear "Fail to allocate bitmap" is not a matplotlib error message, so we need more information about your environement. What backend are you using? If your goal is just to save plots, set it to `"agg"` and avoid opening any windows. – Jody Klymak May 02 '21 at 19:45
  • My environment is Anaconda on Windows 10. Python 3.9.2. I minimized my code to only 1 line in order to focus on the problem, this line is "fig, ax = plt.subplots(1)". I loop this line and I get the error message "Fail to allocate bitmap" after 185 times into the loop. I also try to print the stack trace but unfortunately I have no any extra information printed. – Waleed ELerksosy May 03 '21 at 03:03