MiniMagick で正方形のアイコン作るやつ

gistfile1.rb

class MiniMagick::Image
  def square(size)
    narrow = self[:width] > self[:height] ? self[:height] : self[:width]
    combine_options do |c|
     c.gravity "center"
     c.crop "#{narrow}x#{narrow}+0+0"
    end
    resize "#{size}x#{size}"
  end
end