Process imagemagick functions not working with Dragonfly::Processor

Question

In my user model I want to resize the image on upload. I am storing the images on amazon s3. Everything worked great and the image displays, uploads, deletes, etc. until I tried to add the after_assign method in the image_accessor block.

Here is the error:

None of the functions registered with Dragonfly::Processor were able to deal with the 
method call thumb

I've followed the tutorials online, and double-checked everything. I figure it is an error with imagemagick or rmagick, but after reinstalling both Im at a loss. My path for $ which convert is /opt/local/bin/convert which I am pretty sure is good that the path shows up.

Any suggestions on how to get process to work? I am running on Snow Leopard, Ruby 1.9.3 and Rails 3.2.5

---

For reference:

Here is my user model:

class User < ActiveRecord::Base

    image_accessor :avatar do
      storage_path{ |file| "#{self.id}/avatar/#{rand(1000)}.#{file.format}" }
      after_assign{ |a| a.thumb!('300x300#') }
    end

  ...

  attr_accessible :name, :location, :avatar, :retained_avatar,
    # Used by Devise
    :email, :password, :password_confirmation, :remember_me, :confirmed_at

  validates_size_of      :avatar, maximum: 5.megabytes, allow_nil: true
  validates_property :format, of: :avatar, 
    in: [ :jpg, :png, :gif ], case_sensitive: false, allow_nil: true, 
    message: "Only .jpg, .png and .gif file formats are supported."

end

Here is my dragonfly initializer

require 'dragonfly'

app = Dragonfly[:images]

app.configure_with(:imagemagick)
app.configure_with(:rails)

app.datastore = Dragonfly::DataStorage::S3DataStore.new

app.datastore.configure do |c|
  c.bucket_name = ENV['S3_BUCKET']
  c.access_key_id = ENV['S3_KEY']
  c.secret_access_key = ENV['S3_SECRET']
  c.url_scheme = 'https' 
end

app.define_macro(ActiveRecord::Base, :image_accessor)

Answer 1

if your file is called :photo, then its after_assign should be after_assign { |a| self.photo = a.thumb('300x300#) }