title: libpng error: Read Error when using matplotlib after setting usetex=True
body: <p>On two different machines running Windows 10, I am getting the error <code>libpng error: Read Error</code> leading to python crashing when trying to plot after setting the option <code>usetex=True</code> in matplotlib. This has worked without problems before on this machine, I am not sure what changed since.</p>
  
  <p>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.</p>
  
  <p>A minimum example, directly after creating a fresh environment with <code>conda create --name libpngtest python=3 matplotlib libpng</code>:</p>
  
  <pre><code>&gt;&gt;&gt; import matplotlib.pyplot as plt
  &gt;&gt;&gt; from matplotlib import rc
  &gt;&gt;&gt; rc('text', usetex=True)
  &gt;&gt;&gt; plt.plot(1,2)
  [&lt;matplotlib.lines.Line2D object at 0x00000193015A8908&gt;]
  &gt;&gt;&gt; plt.show()
  </code></pre>
  
  <p>At this point sometimes the python console just crashes out without any message, but I have also seen <code>libpng error: Read Error</code> printed before it crashes. Inside a jupyter notebook/lab, the kernel will restart and <code>libpng error: Read Error</code> appears in the terminal where jupyter is running between jupyter messages.</p>
  
  <p>At this point I am not sure if this is a python problem or a TeX problem (I have MikTeX 2.9 installed, which seems to be running fine), but would appreciate any hints you may have.</p>
  
  <hr>
  
  <p>Edit: The output after setting <code>plt.set_loglevel("debug")</code> is:</p>
  
  <pre><code>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       -&gt;
  DEBUG:matplotlib.texmanager:text.latex.unicode  : None       -&gt; True
  DEBUG:matplotlib.texmanager:text.latex.preview  : None       -&gt; False
  DEBUG:matplotlib.texmanager:font.family         : None       -&gt; ['sans-serif']
  DEBUG:matplotlib.texmanager:font.serif          : None       -&gt; ['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       -&gt; ['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       -&gt; ['Apple Chancery', 'Textile', 'Zapf Chancery', 'Sand', 'Script MT', 'Felipa', 'cursive']
  DEBUG:matplotlib.texmanager:font.monospace      : None       -&gt; ['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
  </code></pre>