jnicklas/carrierwave — pull request #649 by Hakon (2012-03-07 14:58:00+00:00)
Title: Fix problem where resize_to_fill would remove the transparency of a png

...and replace it with the default background color.

This happens when the -extent command crops the image.

From the http://www.imagemagick.org/Usage/crop/#extent :

> Note that "-extent" works by using the same 'overlay' technique that both the Border and Frame operators uses. As such by default using it with a image containing transparency will replace the transparency with the current "-background" color.