libpng error: Read Error when using matplotlib after setting usetex=True

[joaocaldeira]

Bug report

Bug summary

On two different machines running Windows 10, I am getting the error libpng error: Read Error leading to python crashing when trying to plot after setting the option usetex=True in matplotlib. This has worked without problems before on these machines, I am not sure what changed since.

Code for reproduction and outcome

A minimum example, directly after creating a fresh environment with conda create --name libpngtest python=3 matplotlib libpng:

>>> import matplotlib.pyplot as plt
>>> from matplotlib import rc
>>> rc('text', usetex=True)
>>> plt.plot(1,2)
[<matplotlib.lines.Line2D object at 0x00000193015A8908>]
>>> plt.show()

At this point sometimes the python console just crashes out without any message, but I have also seen libpng error: Read Error printed before it crashes. Inside a jupyter notebook/lab, the kernel will restart and libpng error: Read Error appears in the terminal where jupyter is running between jupyter messages.

Matplotlib version

I have tried installing different libpng versions (1.6.32, 1.6.34, 1.6.36, 1.6.37) but all of them lead to the same outcome.

• Operating system: Windows 10
• Matplotlib version: 3.1.1 (but have tried with different versions, as changing the version of libpng results in different matplotlib versions)
• Matplotlib backend: Qt5Agg
• Python version: 3.7.6, but see comment under matplotlib version
• Other libraries: libpng
• Other software: MiKTeX 2.9

debugger output

The output after setting plt.set_loglevel("debug") is:

DEBUG:matplotlib.texmanager:serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: serif, font: Computer Modern Roman, info: ('cmr', '')
DEBUG:matplotlib.texmanager:sans-serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:sans-serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: sans-serif, font: Computer Modern Sans Serif, info: ('cmss', '')
DEBUG:matplotlib.texmanager:cursive font is not compatible with usetex.
DEBUG:matplotlib.texmanager:cursive font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: cursive, font: Zapf Chancery, info: ('pzc', '\\usepackage{chancery}')
DEBUG:matplotlib.texmanager:monospace font is not compatible with usetex.
DEBUG:matplotlib.texmanager:monospace font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: monospace, font: Computer Modern Typewriter, info: ('cmtt', '')
DEBUG:matplotlib.texmanager:following keys changed: ['text.latex.preamble', 'text.latex.unicode', 'text.latex.preview', 'font.family', 'font.serif', 'font.sans-serif', 'font.cursive', 'font.monospace']
DEBUG:matplotlib.texmanager:text.latex.preamble : None       ->
DEBUG:matplotlib.texmanager:text.latex.unicode  : None       -> True
DEBUG:matplotlib.texmanager:text.latex.preview  : None       -> False
DEBUG:matplotlib.texmanager:font.family         : None       -> ['sans-serif']
DEBUG:matplotlib.texmanager:font.serif          : None       -> ['DejaVu Serif', 'Bitstream Vera Serif', 'Computer Modern Roman', 'New Century Schoolbook', 'Century Schoolbook L', 'Utopia', 'ITC Bookman', 'Bookman', 'Nimbus Roman No9 L', 'Times New Roman', 'Times', 'Palatino', 'Charter', 'serif']
DEBUG:matplotlib.texmanager:font.sans-serif     : None       -> ['DejaVu Sans', 'Bitstream Vera Sans', 'Computer Modern Sans Serif', 'Lucida Grande', 'Verdana', 'Geneva', 'Lucid', 'Arial', 'Helvetica', 'Avant Garde', 'sans-serif']
DEBUG:matplotlib.texmanager:font.cursive        : None       -> ['Apple Chancery', 'Textile', 'Zapf Chancery', 'Sand', 'Script MT', 'Felipa', 'cursive']
DEBUG:matplotlib.texmanager:font.monospace      : None       -> ['DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Computer Modern Typewriter', 'Andale Mono', 'Nimbus Mono L', 'Courier New', 'Courier', 'Fixed', 'Terminal', 'monospace']
DEBUG:matplotlib.texmanager:RE-INIT
old fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.texmanager:serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: serif, font: Computer Modern Roman, info: ('cmr', '')
DEBUG:matplotlib.texmanager:sans-serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:sans-serif font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: sans-serif, font: Computer Modern Sans Serif, info: ('cmss', '')
DEBUG:matplotlib.texmanager:cursive font is not compatible with usetex.
DEBUG:matplotlib.texmanager:cursive font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: cursive, font: Zapf Chancery, info: ('pzc', '\\usepackage{chancery}')
DEBUG:matplotlib.texmanager:monospace font is not compatible with usetex.
DEBUG:matplotlib.texmanager:monospace font is not compatible with usetex.
DEBUG:matplotlib.texmanager:family: monospace, font: Computer Modern Typewriter, info: ('cmtt', '')
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\1acea6f6c115d0ec7a634ed0529287b9.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.dviread:['kpsewhich', 'cmss10.tfm']
DEBUG:matplotlib.dviread:stdout:
b'C:/Program Files/MiKTeX 2.9/fonts/tfm/public/cm/cmss10.tfm\r\n'
DEBUG:matplotlib.dviread:stderr:
b''
DEBUG:matplotlib.dviread:opening tfm file C:/Program Files/MiKTeX 2.9/fonts/tfm/public/cm/cmss10.tfm
DEBUG:matplotlib.dviread:lh=18, bc=0, ec=127, nw=52, nh=16, nd=11
DEBUG:matplotlib.dviread:['kpsewhich', 'cmss10.vf']
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\d598be7bdc6e0eeebdc83c75321a7705.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.dviread:['kpsewhich', 'cmr10.tfm']
DEBUG:matplotlib.dviread:stdout:
b'C:/Program Files/MiKTeX 2.9/fonts/tfm/public/cm/cmr10.tfm\r\n'
DEBUG:matplotlib.dviread:stderr:
b''
DEBUG:matplotlib.dviread:opening tfm file C:/Program Files/MiKTeX 2.9/fonts/tfm/public/cm/cmr10.tfm
DEBUG:matplotlib.dviread:lh=18, bc=0, ec=127, nw=36, nh=16, nd=10
DEBUG:matplotlib.dviread:['kpsewhich', 'cmr10.vf']
DEBUG:matplotlib.dviread:['kpsewhich', 'cmmi10.tfm']
DEBUG:matplotlib.dviread:stdout:
b'C:/Program Files/MiKTeX 2.9/fonts/tfm/public/cm/cmmi10.tfm\r\n'
DEBUG:matplotlib.dviread:stderr:
b''
DEBUG:matplotlib.dviread:opening tfm file C:/Program Files/MiKTeX 2.9/fonts/tfm/public/cm/cmmi10.tfm
DEBUG:matplotlib.dviread:lh=18, bc=0, ec=127, nw=98, nh=15, nd=9
DEBUG:matplotlib.dviread:['kpsewhich', 'cmmi10.vf']
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\1acea6f6c115d0ec7a634ed0529287b9.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\14cf46b44d83e91d3e4f12cc60007df3.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\1acea6f6c115d0ec7a634ed0529287b9.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\217de38979bbb592496a29d181b7bbc4.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\1acea6f6c115d0ec7a634ed0529287b9.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\3233f296f4d6994ca99a0d418d6458d8.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\1acea6f6c115d0ec7a634ed0529287b9.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.dviread:Dvi: C:\Users\...\.matplotlib\tex.cache\e2c00e1750b187927439ebc0ca3a1a38.dvi
DEBUG:matplotlib.dviread:Dvi._xxx: encountered special: papersize=5203.43999pt,5203.43999pt
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e
DEBUG:matplotlib.texmanager:fontconfig: sans-serifcmrcmsspzccmttd41d8cd98f00b204e9800998ecf8427e

[anntzer]

Matplotlib master (and the future 3.2) no longer uses libpng (but Pillow instead) so this is only a 3.1.x thing; may be worth seeing what happens with e.g. the latest 3.2.0 rc release.

[joaocaldeira]

Well, installing matplotlib 3.2.0-rc1 definitely changed things. Now the commands above triggered the installation of two TeX packages, cm-super and oberdiek, though the file it is looking for in oberdiek, ifvtex.sty, is no longer in oberdiek, so I'm stuck again. That's clearly a TeX issue though. Will circle back once I figure that one out.

[joaocaldeira]

Ok, MiKTeX's (user-specific) package database needed updating, and after installing the cm-super and ifvtex packages, plotting works.

I'm not sure whether to close this issue. Plotting still only works on 3.2.0.

[anntzer]

So to confirm, the thing still fails on 3.1.x even after fixing your miktex install?

[joaocaldeira]

Yes, the behavior on 3.1.1 has not changed.

[tacaswell]

Given that this is fixed in 3.2 and the release of 3.2 in imminent, I'm going to close this as fixed (for 3.2). Thank you for reporting this @joaocaldeira and sorry for the trouble.