Why does Image Magick fail to read fonts? I'm trying to create a simple contact sheet of all the photos in a directory using Montage:

$ montage -font Helvetica -pointsize 10 *.png contact_sheet.jpg


However, I keep getting a error reading the font file:

montage: unable to read font `Helvetica' @ error/annotate.c/RenderFreetype/1239.


I've tried several fonts, including Arial, and putting the font name in quotes, but get the same error.

Leaving the -font option blank returns:

unable to read font '(null)' @ error/annotate.c/RenderFreetype/1239
I've found that installing GhostScript fixes the problem. Using brew: brew install gs