module MiniMagickClip

# File lib/mini_magick_clip.rb, line 6
def mask mask_path
  manipulate! do |img|
    img.format 'png'

    mask = ::MiniMagick::Image.open mask_path
    mask.resize([img[:width], img[:height]].join("x"))

    masked = img.composite(mask, 'png') do |i|
      i.alpha "set"
      i.compose 'DstIn'
    end
  end
end