If a preview cannot be generated, the IO stream that is captured is empty, resulting in a 0-byte preview file being generated and stored in the Active Storage service.
We came across this because Poppler was failing to generate previews of some PDFs, resulting in 0-byte files. Resizing those "previews" then resulted in a MiniMagick error. The MiniMagick error feels like the right end result if it's attempted on a 0-byte file, what doesn't feel right is `Previewer` proceeding normally if the child process that attempted to capture a preview exited unsuccessfully.
Now, if the previewer child process exits with a non-0 status code, we raise an exception.
When a PDF is used for both printing and displaying. It will most likely
contain a crop box in order to hide print margins when displaying the PDF.
Use Poppler's parameter to automatically use the crop box (visible box)
rather than the media box (printable box) in order to remove those margins
when drawing the PDF.
See https://manpages.debian.org/testing/poppler-utils/pdftoppm.1.en.html
mutool is licensed under the Affero GPL, which has strict distribution requirements.
Poppler is licensed under the more liberal GPL, making it a good alternative for those who can't use mutool.
