SyntaxError: not a PNG file

[BexTuychiev]

I can't push a notebook to Medium because of the following error:

Traceback (most recent call last):
  File "\\wsl$\Ubuntu\home\bexgboost\articles\deploy_to_medium.py", line 4, in <module>
    jtm.publish('2023/1_january/3_synthetic_data_generators/notebook.ipynb',
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\jupyter_to_medium\_publish_to_medium.py", line 300, in publish
    p.main()
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\jupyter_to_medium\_publish_to_medium.py", line 218, in main
    self.md, self.image_data_dict = self.create_markdown()
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\jupyter_to_medium\_publish_to_medium.py", line 121, in create_markdown
    no_ex_pp.preprocess(self.nb, self.resources)
  File "C:\Users\bex\anaconda3\envs\articles\lib\site-packages\nbconvert\preprocessors\base.py", line 69, in preprocess
    nb.cells[index], resources = self.preprocess_cell(cell, resources, index)
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\jupyter_to_medium\_preprocesors.py", line 148, in preprocess_cell
    output['data'] = {'image/png': converter(html)}
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\jupyter_to_medium\_screenshot.py", line 169, in run
    img = self.take_screenshot()
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\jupyter_to_medium\_screenshot.py", line 121, in take_screenshot
    img = mimage.imread(buffer)
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\matplotlib\image.py", line 1560, in imread
    with img_open(fname) as image:
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\PIL\ImageFile.py", line 116, in __init__
    self._open()
  File "C:\Users\bex\AppData\Roaming\Python\Python39\site-packages\PIL\PngImagePlugin.py", line 712, in _open
    raise SyntaxError("not a PNG file")
SyntaxError: not a PNG file

What might be the reason for this? Plots (I do have some from Seaborn). The problem is only with that notebook, other notebooks are pushing fine. Here is a link to the notebook.

@tdpetrou, can you please take a look if you have time?

[mjam03]

Hi there,

Sorry for not getting back to you sooner. I've actually seen that our tests are now failing only on windows with this issue. It seems to be due to:

• plots get screenshotted using Chrome
• that should produce a png
• the matplotlib.image module expects this and fails otherwise

I don't have a windows so can't test this and can't find anything around the web on it but will keep searching this week and try to get fixed.

Mark

[FoamoftheSea]

I was having this problem in 0.2.13 on Windows. The subprocess call to chrome.exe to take the screenshot was creating an empty PNG image, but I was able to fix that by taking lines 115-126 out of the context manager block in _screenshot.py.

This made the image come out larger than 0KB, and fixes the downstream issue.

[FoamoftheSea]

@mjam03 Created PR #79