Can't get OpenCV to install in Heroku for "smart" crops

[gesteves]

The closest I've gotten is using this buildpack (forked from here), which compiles successfully in Heroku. However, the build ends with:

-----> Compressing... 
 !   Compiled slug size: 557.8MB is too large (max is 300MB).
 !   See: http://devcenter.heroku.com/articles/slug-sizefailed
 !     Push failed: slug archive could not be created
 !     Please try pushing again.
 !     If the problem persists, see http://help.heroku.com/ and provide Request ID f139aace-bc70-4695-b1e4-bce73ad304c6.

I'm out of ideas, so smart crops don't work for now.

¯_(ツ)_/¯