Guide: Batch convert PDFs to JPGs

A frequent chore I am called upon to perform is generating JPGs of book covers from PDFs. This is especially tedious as many of the covers belong to series. Consequently, I researched a way to perform this task on the command line via ImageMagick. This workflow allows me to process PDFs in batches via xargs or by writing a series of commands in Vim which can be run line-by-line via :w !sh. It is much faster than processing the images by hand.

Note: This method pairs nicely with this InDesign script for batch generating product mockups.

First, I must convert each PDF to a high-quality JPG.¹ I remove the alpha channel and set the background to white. Otherwise, transparent parts of the image may appear as other colors.²

magick -verbose \
       -density 300 \
       input.pdf \
       -background white \
       -alpha remove \
       -alpha off \
       -quality 100 \
       -flatten \
       output-f-lg.jpg

I also typically want a 600px wide version of every image:³

magick input-f-lg.jpg -resize 600 output-f-sm.jpg

Footnotes:

See this thread on Stack Overflow for more info on converting PDFs to JPGs with ImageMagick: https://stackoverflow.com/questions/6605006/convert-pdf-to-image-with-high-resolution

See this thread on Stack Overflow for more info on dealing with transparent images via ImageMagick: https://stackoverflow.com/questions/2322750/replace-transparency-in-png-image-with-white-background

For more info on resizing with ImageMagick, see this Stack Overflow thread: https://github.com/xKeNcHii/Mockup-Automation-Script