Steps to reproduce

Given a Rails 5.2.0beta2 app using ActiveStorage and mini_magick, attach a rectangular image to a model and then call it with <image>.variant(thumbnail: '100x100^', gravity: 'center', extent: '100x100')

Expected behavior

The image returned is 100px square with the excess cropped and the image centered

(centered cropping is described here and gravity is shown to work with mini_magick here)

Actual behavior

The image returned is 100px square with excess cropped, however the image is anchored on the upper left

System configuration

Rails version: 5.2.0beta2

Ruby version: 2.4.2

mini_magick version: 4.8.0

ImageMagick version: 7.0.7-15