carrierwave_fog.rb

CarrierWave.configure do |config|
  config.fog_credentials = {
    :provider               => 'AWS',       # required
    :aws_access_key_id      => 'my_access_key',       # required
    :aws_secret_access_key  => 'my_secret_access_key',       # required
    :region                 => 'us-east-1'  # optional, defaults to 'us-east-1'
  }
  config.fog_directory  = 'my_bucket_name'                     # required
  config.fog_host       = 'https://my_bucket_name.s3.amazonaws.com'            # optional, defaults to nil
  config.fog_public     = false                                   # optional, defaults to true
  config.fog_attributes = {'Cache-Control'=>'max-age=315576000'}  # optional, defaults to {}
  config.max_file_size     = 30.megabytes        # defaults to 5.megabytes
  config.upload_expiration = 30.minutes              # defaults to 10.hours
end

gemfile

source 'http://rubygems.org'

gem 'rails', '3.0.9'

# Bundle edge Rails instead:
# gem 'rails', :git => 'git://github.com/rails/rails.git'

gem 'mysql2', '~> 0.2.6'
gem 'rake', '0.8.7'
gem "aws-s3", :require => 'aws/s3'
gem 'carrierwave'
gem 'carrierwave_direct'
gem 'nokogiri'

image_uploader.rb

class ImageUploader < CarrierWave::Uploader::Base

  #storage :fog
  
  include CarrierWaveDirect::Uploader

end