This is a Heroku buildpack for vendoring the ImageMagick binaries into your project.
On heroku you configure this buildpack like this:
heroku config:set IMAGE_MAGICK_HOST=http://www.imagemagick.org/download/releases/
heroku config:set IMAGE_MAGICK_VERSION=6.9.3-10
heroku config:set IMAGE_MAGICK_SHA=e33f021c879f31703f9e620f578ccf7d221a34941589da4bbe967b16a814336a
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.
The "SHA" is a SHA-256 checksum. This ensures that no one can modify the code you install on your servers, e.g. by hacking the code repository and uploading a version of ImageMagick that includes harmful code. You will of course have to ensure that the version you get the shasum for isn't already hacked :)