This is a Heroku buildpack for vendoring the ImageMagick binaries into your project.
On heroku you configure this buildpack like this: heroku config:set GHOSTSCRIPT_VERSION=ghostscript-9.26 heroku config:set LIBDE265_VERSION=v1.0.3 heroku config:set LIBHEIF_VERSION=v1.3.2 heroku config:set IMAGEMAGICK_VERSION=7.0.8-27
If you use this buildpack directly (e.g. in CI) you have to create files on disk that bin/compile can read. They have the same names as the environment variables and the same contents. Look at the script to see what it expects.
In some Auctionet projects, see script/circleci/install_imagemagick.sh for how to edit these files.