Non standard PDF generated by PDF Complete or JRAPublish aren't readable by GhostScript. The issue seems to be related to fonts.
[ Steps to reproduce bug ]
- Go to a non standard PDF file, e.g. [[Commons:File:Electromagnetic Field.pdf]]
- Open the thumbnail (e.g. right click > view image) - https://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Electromagnetic_Field.pdf/page1-463px-Electromagnetic_Field.pdf.jpg
[ Error message ]
Error creating thumbnail: **** Warning: can't process font stream, loading font by the name.
- Error reading a content stream. The page may be incomplete.
- File did not complete the page properly and may be damaged.
- This file had errors that were repaired or ignored.
- The file was produced by:
- >>>> PDF Complete 3.5.310.2002 <<<<
- Please notify the author of the software that produced this
- file that it does not conform to Adobe's published PDF
convert: no decode delegate for this image format `/tmp/magick-80d5LrYy' @ error/constitute.c/ReadImage/532.
convert: missing an image filename `/tmp/transform_34b4e206409f-1.jpg' @ error/convert.c/ConvertImageCommand/3011.
[ Side note ]
This upstream bug is related but not identical to our issue: