acts_as_blog

In my current app, I’m using paperclip for handling images.

Paperclip includes the option for id_partition, but I prefer an hashed stucture (descriped in my first blog).

For example, the image url looks like

http://my_url/medias/0d/898/0d898414092854eacbf27f8db12ce4db_avatar.jpg

This is the basic configuration in my Media-Model

  # paperclip
  has_attached_file( :source,
    :styles => {
      :original => '1600x1600>',
      :avatar => '50x50#' },
    :storage => :filesystem,
    :url => "/:class/:hashed_public_id/:public_id_:style.:extension",
    :path => ":rails_root/public/:class/:hashed_public_id/:public_id_:style.:extension"
  )

To set the public id, I used the following code and create an md5-hash.
Surely, you can use what you want, for example ActiveSupport::SecureRandom.hex(32).
My set_public_id creates a random string like “6e374ca829eaead5090f6cdd26c08017″.

  def set_public_id
    self.public_id = Digest::MD5.hexdigest(self.source_file_name + self.source_file_size.to_s + rand.to_s + Time.now.to_i.to_s)
  end

For using hashed_public_id or public_id in the paperclip configuration :url => “/:class/:hashed_public_id/:public_id_:style.:extension”, you must set the following attachment interpolations.

  Paperclip::Attachment.interpolations[:public_id] = lambda do |attachment, style|
    # e. g. "6e374ca829eaead5090f6cdd26c08017"
    attachment.instance.public_id
  end

  Paperclip::Attachment.interpolations[:hashed_public_id] = lambda do |attachment, style|
    # e. g. "6e/374"
    File.join(attachment.instance.public_id[0..1], attachment.instance.public_id[2..4])
  end

Furthermore, I need to rotate an image. Therefore, I used the follwing code.
All styles of the image (e. g. original, avatar) will be rotated.

require 'RMagick'
def rotate(degrees)

    if(degrees.class == Fixnum && degrees % 90 == 0)
      each_attachment do |n, a|
        self.source.styles.each do |styles|
          image_path = a.path(styles.first)

          image   = Magick::ImageList.new(image_path)
          image   = image.rotate(degrees)
          image.write(image_path)
        end
        return true
      end
    end
    nil

  end

Helpful links:

• http://addictedtonew.com/archives/127/rotating-images-with-rmagick-and-ruby-on-rails/
• http://jimneath.org/2008/04/17/paperclip-attaching-files-in-rails/
• http://wiki.github.com/thoughtbot/paperclip/interpolations
• http://thewebfellas.com/blog/2008/11/2/goodbye-attachment_fu-hello-paperclip

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