This has been (manually) forked from ello/heroku-buildpack-imagemagick.
The main difference is that it actually supports reading environment variables to set the version of ImageMagick to compile.
This is a Heroku buildpack for vendoring the ImageMagick binaries into your project.
Rather than pulling down binary dependencies from a package manager and extracting them into place, this buildpack compiles Imagemagick from source the first time an app is built with it. The compiled binaries are cached for future builds, so this penalty is only incurred once.
This has the downside of a (potentially very long) deploy time for the first push, with the benefit of a less-fragile build product that's somewhat less likely to break due to platform and dependency shifts. Or at least, that's the hope!
This buildpack is tested primarily against the cedar-14 stack. Currently, a workaround is required to make it work on the newer heroku-16 stack - see ello/heroku-buildpack-imagemagick#17 for details.