I have the same problem as reported Lyx, Error Converting to Loadable Format for PDFs but I am using Ubuntu 18.04, and solutions are only described for Windows and MacOS.

Here are the stderr messages if I run LyX from the command line:

convert-im6.q16: not authorized `/tmp/lyx_tmpdir.mJCcewM29047/gconverts29047.eps' @ error/constitute.c/ReadImage/412.
convert-im6.q16: no images defined `/tmp/lyx_tmpdir.mJCcewM29047/gconverts29047.png' @ error/convert.c/ConvertImageCommand/3258.

The LyX wiki solutions https://wiki.lyx.org/LyX/FiguresInLyX also don't apply, since my versions are:

ImageMagick 6.9.7-4

Ghostscript 9.25 (2018-09-13)

My /etc/ImageMagick-6/policy.xml looks like:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE policymap [
<!ELEMENT policymap (policy)+>
<!ELEMENT policy (#PCDATA)>
<!ATTLIST policy domain (delegate|coder|filter|path|resource) #IMPLIED>
<!ATTLIST policy rights CDATA #IMPLIED>
<!ATTLIST policy pattern CDATA #IMPLIED>
<!ATTLIST policy value CDATA #IMPLIED>
...(comments excised for brevity)...
  <!-- <policy domain="resource" name="temporary-path" value="/tmp"/> 
  <policy domain="resource" name="memory" value="256MiB"/>
  <policy domain="resource" name="map" value="512MiB"/>
  <policy domain="resource" name="width" value="16KP"/>
  <policy domain="resource" name="height" value="16KP"/>
  <policy domain="resource" name="area" value="128MB"/>
  <policy domain="resource" name="disk" value="1GiB"/>
  <!-- <policy domain="resource" name="file" value="768"/> -->
  <!-- <policy domain="resource" name="thread" value="4"/> -->
  <!-- <policy domain="resource" name="throttle" value="0"/> -->
  <!-- <policy domain="resource" name="time" value="3600"/> -->
  <!-- <policy domain="system" name="precision" value="6"/> -->
  <!-- not needed due to the need to use explicitly by mvg: -->
  <!-- <policy domain="delegate" rights="none" pattern="MVG" /> -->
  <!-- use curl -->
  <policy domain="delegate" rights="none" pattern="URL" />
  <policy domain="delegate" rights="none" pattern="HTTPS" />
  <policy domain="delegate" rights="none" pattern="HTTP" />
  <!-- in order to avoid to get image with password text -->
  <policy domain="path" rights="none" pattern="@*"/>
  <policy domain="cache" name="shared-secret" value="passphrase" stealth="true"/>
  <!-- disable ghostscript format types -->
  <policy domain="coder" rights="none" pattern="PS" />
  <policy domain="coder" rights="none" pattern="EPI" />
  <policy domain="coder" rights="read|write" pattern="PDF" />
  <policy domain="coder" rights="none" pattern="XPS" />
  <policy domain="coder" rights="read|write" pattern="LABEL" />
  • 1
    I had a similar issue on Ubuntu 18.04. This thread helped me solve the problem: stackoverflow.com/questions/42928765/… – scottkosty Nov 28 '18 at 17:43
  • @scottkosty Curiously, my policy.xml file already looks like the updated version. – CPBL Nov 28 '18 at 21:12
  • Can you convert the PDF on the command line? Can you give the terminal output, if there is an error, when you try the conversion on the command line (i.e., outside of LyX)? – scottkosty Nov 28 '18 at 23:03
  • convert myPDFfigure.pdf myPDFfigure.png works perfectly on the command line. I'm actually not clear on what the conversion that LyX needs is. PDF->png is not listed in the LyX converter definitions. – CPBL Nov 30 '18 at 3:22
  • 1
    Great! Go ahead and add & accept your answer to mark this is solved. Glad it's sorted out! – scottkosty Dec 1 '18 at 3:31

The solution was to edit ImageMagick's policy.xml file. Even though it was a PDF that I supplied to LyX, and LyX ends up with a PNG, it was lacking permissions for EPS (PS).

Thus, in /etc/ImageMagick-6/policy.xml I changed

<policy domain="coder" rights="none" pattern="PS" />


<policy domain="coder" rights="read|write" pattern="PS" />

Diagnosis all thanks to @ScottKosty; see comments following my question.

| improve this answer | |
  • Just worked for me on Linux Mint 19.3. – jaia Jul 22 at 1:55

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