Example of using carrierwave to manage file uploads

avatar_uploader.rb

require 'carrierwave/processing/mime_types'

class AvatarUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick
  include CarrierWave::Processing::MiniMagick
  include CarrierWave::MimeTypes

  # Changes the file content_type using the mime-types gem
  process :set_content_type

  # Strips out all embedded information from the image
  process :strip

  # Changes the image encoding format to the given format
  process :convert => 'jpg'


  # Adds a new version to the uploader
  version :large do
    # Resize the image to fit within the specified dimensions while retaining
    # the original aspect ratio. Will only resize the image if it is larger 
    # than the specified dimensions. The resulting image may be shorter or 
    # narrower than specified in the smaller dimension but will not be larger 
    # than the specified values.
    process :resize_to_limit => [600, 450]
  end

  version :profile do
    # Resize the image to fit within the specified dimensions while retaining
    # the aspect ratio of the original image. If necessary, crop the image in the
    # larger dimension.
    process :resize_to_fill => [250, 250]
  end

  version :thumb do
    process :resize_to_fill => [60, 60]
  end

  # allowed file extensions can be listed in extension_white_list method. 
  # Trying to upload a file with a different extension 
  # would result in displaying an error.
  def extension_white_list
    %w(jpg jpeg gif png)
  end

  # Location where the uploaded files are stored can be changed 
  # by overriding the store_dir method
  def store_dir
    "public/#{model.class.to_s.underscore}/#{model.uuid}/avatar"
  end

  # For storing files outside the project root folder, 
  # cache_dir should be overriden
  def cache_dir
    "#{Rails.root}/tmp/uploads"
  end

  
  def default_url
    "application/default_avatar_#{version_name}.png"
  end

end