Hi everyone, just a tip for an issue I hit. Had both imagemagick and ghostscript installed but was not getting thumbnails generated in the files app.
There was an error in the system log:
Image processing failed to create thumbnail, convert-im6.q16: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/421. convert-im6.q16: no images defined `da...
Based on a stack overflow answer, and other pages, it looked like a policy restricting PDF handling based on a ghostscript CVE bug in versions < 9.2.4. The Debian I am using has GS v10 so its safe to disable this policy again for an internal app not exposed to user uploaded content. You will have to make your own security/risk decision which is probably 'no' if you handle PS based files from unknown sources.
Thumbnails work now, although I had to re-upload the file to trigger the thumbnail generation. Couldn't find a scheduled task or action to manually regenerate thumbnails for already uploaded files which is no biggie as it is an edge case.