In the off chance this helps someone else: I started building my own ImageMagick after the project changed their static binary to an AppImage, which doesn’t work very well.

As with all programs from that age, every feature is configurable, and it’s non-trivial to get it compiled with support for more unusual formats like HEIC. I thought I’d succeeded, but have for months been using a build that couldn’t read HEIC, and it’d only been working by virtue of me not uploading a HEIC in a while.

My ./configure invocation looked right:

./configure --with-heic=yes --with-webp=yes ...

But it’d been silently failing:

Delegate Library Configuration:
  ...
  Ghostscript lib   --with-gslib=no	 no
  Graphviz          --with-gvc=yes	 no
  HEIC              --with-heic=yes  no
  ...

Yes to HEIC, but actually … no.

There’s GitHub issues around with the same problem. It can have a variety of causes, but probably means that configure couldn’t load one of the dependencies for HEIC properly (libde265 and libheif).

ImageMagick’s build process silently swallows problems, so it’s necessary to go to configure.log to find out what happened. Digging into mine, I found that I was missing another dependency called dav1d, which turns out to be an AV1 decoder from the VideoLAN project.

configure:31871: $PKG_CONFIG --exists --print-errors "libheif >= 1.4.0"
Package dav1d was not found in the pkg-config search path.
Perhaps you should add the directory containing `dav1d.pc'
to the PKG_CONFIG_PATH environment variable

I fixed the problem with:

apt-get install libdav1d-dev