Graphics problems with LyX on Linux Mint

Graeme duneistein at
Sat Mar 21 16:26:15 UTC 2020

>> On 3/18/20 3:19 PM, Graeme wrote:
>>  I currently use Linux Mint 18.3. Recently I upgraded to LyX using the PPA available at
>> xenial main
>>  Since this upgrade there have been problems with the display of EPS and PDF graphics files in the main LyX editor window, and with the export of files containing PNG and JPEG bitmap images.
>>  These problems are not evident with LyX on Windows 10, nor were they present with LyX 2.3.3 on Linux Mint 18.3.
>>  Specifically:
>>  1. When including a graphic with either EPS or PDF format, the graphic is not displayed in the main LyX editor window, but instead there is an outline box with the EPS or PDF filename, and below it the error message: Error converting to loadable format.
>>  The graphic does appear correctly in a PDF file exported using either ps2pdf or pdflatex.
>>  2. When including a graphic with PNG or JPEG format, the graphic is displayed correctly in the main LyX editor window, but when attempting to export the LyX file to Postscript, PDF (using ps2pdf), or even just plain LaTeX, an error pop-up window appears with the title:
>>  LyX: Cannot convert file
>>  and the message: 
>>  No information for converting png format files to eps. Define a converter in the preferences or No information for converting jpg format files to eps. Define a converter in the preferences.
>>  The PNG and JPEG graphics do appear correctly in a PDF file exported using pdflatex, but attempting to export with ps2pdf fails.
>>  When exporting the Progress Log window shows the following messages for a graphic in PNG format:
>>     python -tt "/usr/share/lyx/scripts/" png "/tmp/lyx_tmpdir.fGfmcihv6288/lyx_tmpbuf0/2_home_graeme_Documents_GraphicsTestCircle.png" eps "/tmp/lyx_tmpdir.fGfmcihv6288/lyx_tmpbuf0/2_home_graeme_Documents_GraphicsTestCircle.eps" convert: not authorized `eps:/tmp/lyx_tmpdir.fGfmcihv6288/lyx_tmpbuf0/2_home_graeme_Documents_GraphicsTestCircle.eps' @ error/constitute.c/WriteImage/1028.
>>     /usr/share/lyx/scripts/ ERROR
>>     Execution of "convert" (276): Systemcall: 'python -tt "/usr/share/lyx/scripts/" png "/tmp/lyx_tmpdir.fGfmcihv6288/lyx_tmpbuf0/2_home_graeme_Documents_GraphicsTestCircle.png" eps "/tmp/lyx_tmpdir.fGfmcihv6288/lyx_tmpbuf0/2_home_graeme_Documents_GraphicsTestCircle.eps"' finished with exit code 1
>>     Error: Cannot convert file
>>  I get similar messages for a graphic file in JPEG format.
>>  My suspicion is that BOTH the problems above may be linked to the use of ImageMagick within, but I am puzzled by the warning message
>>  "convert: not authorized"
>>  in the fragment above, suggesting it may be something to do with file or folder permissions. However, this does not explain why everything seemed to work OK with LyX 2.3.3 on Mint 18.3
>>  On Mint 18.3 the system-wide installation of ImageMagick is:
>>  ImageMagick 6.8.9-9 Q16 x86_64 2019-11-12
>>  On Windows 10, the LyX2.3.4.3 installer comes bundled with a later version:
>>  ImageMagick 7.0.9-19 Q16 x86 2020-01-26
>>  which explicitly lists built-in support for gslib and ps, but ImageMagick 6 does not list these among its "Delegates".
>>  I would welcome advice on how to fix these problems.
>>  Graeme

> Confirmed here (same OS and LyX version). Turns out it's a security issue related to ImageMagick. See this post <> for the gory details. If you're willing to take the risk (I am), you can follow the suggestions in the post, but there may be a quicker way. Wander over to /etc/Imagick-6 and list the directory. You should see policy.xml and policy.xml.dpkg-old. They former is the higher security/problematic policy file in force, and the .dpkg-old version is the looser, less secure (but more LyX friendly) version. As root, give the new one a new name or extension to keep it (or delete it if you will) and move or copy the .dpkg-old version to policy.xml. Worked for me.
> Paul

Thanks, Paul, for your quick and helpful reply.
Unfortunately, in my Mint etc/ImageMagick-6 folder there was only 
policy.xml with no .dpkg-old version with which to compare or replace it.

I followed the link you supplied, had a look at the documentation for 
ImageMagick, and at the policy.xml file bundled with LyX for Windows, 
but the syntax and terminology of policy.xml files remains rather 
obscure to me.

Since it's the effect of these security policies on the behaviour of 
ImageMagick with EPS (and PS) files that matters. I've made small 
changes to the ImageMagick-6 version that allow the convert command to 
operate as desired on EPS and PDF files.

The key code fragment in /etc/ImageMagick-6/policy.xml is in the 
<policymap> section of the file:

<!-- disable ghostscript format types -->
<policy domain="coder" rights="none" pattern="PS" />
<policy domain="coder" rights="none" pattern="PS2" />
<policy domain="coder" rights="none" pattern="PS3" />
<policy domain="coder" rights="none" pattern="EPS" />
<policy domain="coder" rights="none" pattern="PDF" />
<policy domain="coder" rights="none" pattern="XPS" />

I modified two lines in this fragment as follows:

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

1. Changing only the PS line allowed the LyX editor window correctly to 
display included graphic files in EPS or PDF format, but 
File/Export/PDF(ps2pdf) still failed with LyX files that included PNG or 
JPEG graphics.

2. Changing only the EPS line resolved the problem of exporting files 
with included PNG or JPEG graphics, but did not allow the LyX editor 
window to display included graphic files in EPS or PDF format.

3. It wasn't necessary to change the PDF line. Not sure why.

4. It seems that changing both the PS and the EPS lines is sufficient to 
resolve both problems, but I don't know whether this is the necessary 
minimum. Is there a better, or safer, way of modifying the file policy.xml?

Finally, I'm surprised that the problem has so far only been reported 
for Linux Mint, prompting the following questions:

a) Does Mint have a much stricter security policy for ImageMagick than 
Ubuntu or other Linux distributions?

b) None of the lines in the <policymap> fragment above appear in the 
policy.xml for ImageMagick 7 that is bundled with LyX in the 
Windows installer. Was that policy.xml crafted specifically to work with 
LyX, and to avoid the problems reported here?


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