class Middleman::Extensions::AutomaticImageSizes

def image_tag(path, params={})
  if !params.key?(:width) && !params.key?(:height) && !path.include?('://')
    real_path = path.dup
    real_path = File.join(config[:images_dir], real_path) unless real_path.start_with?('/')
    file = app.files.find(:source, real_path)
    if file && file[:full_path].exist?
      begin
        full_path = file[:full_path].to_s
        width, height = ::FastImage.size(full_path, raise_on_failure: true)
        # Check for @2x and @3x image
        retina = full_path.match(/@(\d)x\.[a-zA-Z]{3,4}$/)
        if retina
          factor = retina[1].to_i
          width /= factor
          height /= factor
        end
        params[:width]  = width
        params[:height] = height
      rescue FastImage::UnknownImageType
        # No message, it's just not supported
      rescue
        warn "Couldn't determine dimensions for image #{path}: #{$ERROR_INFO.message}"
      end
    end
  end
  super(path, params)
end

def initialize(app, options_hash={}, &block)
  super
  # Include 3rd-party fastimage library
  require 'fastimage'
end