Default images for carrierwave using placeholder.it

default_image.rb

class DefaultImage

  def initialize(width, height)
    @width = width
    @height = height
  end

  def create(options={})
    name = options[:name] || "image_#{Time.now.to_i}"
    default_format = 'png'
    format = options[:format] || default_format
    url   = 'http://placehold.it/' + @width.to_s + 'x' + @height.to_s
    image = MiniMagick::Image.open(url)
    image.format format
    path = "#{Rails.root}/app/assets/images/fallback/" + [name, format].join('.')
    image.write path
  end
end