Cfrgtkky

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 name CDATA #IMPLIED>

<!ATTLIST policy rights CDATA #IMPLIED>

<!ATTLIST policy pattern CDATA #IMPLIED>

<!ATTLIST policy value CDATA #IMPLIED>

]>

<!--

...(comments excised for brevity)...

-->

<policymap>

  <!-- <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" />

</policymap>

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" />

to

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

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