Graphics problems with LyX on Linux Mint

Paul A. Rubin parubin73 at
Sat Mar 21 16:57:27 UTC 2020

On 3/21/20 12:26 PM, Graeme wrote:
>>> 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?
> Graeme

Interesting that you did not have the old version of the policy file. 
FWIW, the old version I have lacks two of the six policy items you 
listed (PS2 and PS3) and simply comments out, rather than modifying, the 
other four.

To answer your first question, Mint gets Imagemagick and associated 
files from the Canonical repositories. (The policy file is in the 
imagemagick-common package.) Honestly, I have no idea where I got the 
older version of the file. It does not appear to have been installed by 
synaptic (or at least synaptic won't admit to having done so.) Possibly 
it came along with something I installed from a PPA.

As to the Windows version, I really don't know, but perhaps the Windows 
version of Imagemagick is less vulnerable to the security problems those 
extra lines are designed to combat? (This would be the first time in my 
experience that Windows was less vulnerable to anything, but there are 
more things in the digital realm than in my philosophy.)


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