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Note: The PDF thumbnail generator is hard-coded to generate a thumbnail from the first page of the PDF.

Possible Errors / Issues

"convert.im6: not authorized" errors

On Ubuntu (possibly other OSes), you may see errors like these when attempting to generate PDF thumbnails:

ERROR filtering, skipping bitstream:
        Item Handle: 1234/5678
        Bundle Name: ORIGINAL
        File Size: 30406135
        Checksum: c1df4b3a4755e9bed956383b61fc5042 (MD5)
        Asset Store: 0
org.im4java.core.CommandException: org.im4java.core.CommandException: convert.im6: not authorized `/tmp/impdfthumb6294641076817830415.pdf' @ error/constitute.c/ReadImage/454.

These may be caused by a change in your ImageMagick policy configuration on your server. 

In Ubuntu, the default "policy.xml" was recently updated to exclude all Ghostscript formats (including PDF, PS, etc).  See this ticket: https://bugs.launchpad.net/ubuntu/+source/imagemagick/+bug/1796563

• This exclusion was implemented to workaround a security vulnerability in Ghostscript reported here: https://www.kb.cert.org/vuls/id/332928
• This vulnerability looks like it may have been fixed in Ghostscript v9.25: https://www.ghostscript.com/doc/9.25/News.htm (Still pending verification – see launchpad ticket linked above)

The newly added lines in the /etc/ImageMagick/policy.xml are these ones:

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

If you wish to re-enable ImageMagick to process Ghostscript format types, you can simply comment out those lines in the configuration file.  Be aware that, as the fix to this vulnerability is not yet verified, you should only do so at your own risk.