gistfile1.rb

class Widget < ActiveRecord::Base
  validates_numericality_of :custom_width

  has_attached_file :file,
      :storage => :s3,
      :s3_credentials => "#{Rails.root}/config/amazon_s3.yml",
      :path => "widgets/:id/file/:normalized_file_file_name_:style.:extension",
      :url => ":s3_alias_url",
      :s3_host_alias => "#{S3Config[:bucket]}",
      :styles => lambda { |attachment| attachment.instance.file_styles }
  # http://blog.wyeworks.com/2009/7/13/paperclip-file-rename
  Paperclip.interpolates :normalized_file_file_name do |attachment, style|
    attachment.instance.normalized_file_file_name
  end
  def normalized_file_file_name
    self.file_file_name[/.*(?=\..+$)/].gsub( /[^a-zA-Z0-9_]/, '_') 
  end
  # Conditional paperclip styles
  # http://groups.google.com/group/paperclip-plugin/browse_thread/thread/983875401f91bb6b?fwc=1
  def file_styles
    styles = {}
    # At the very least, every image is going to be resized to a thumbnail
    styles[:thumb] = { :geometry => '100x67#', :source_file_options => "-resample 72"}
    # Then, if a there is a custom width set, resize that too
    if !custom_width.blank?
      styles[:custom] = { :geometry => "#{custom_width}x9999", :source_file_options => "-resample 72"}
    end
    return styles
  end
  # This halts the processing of the styles unless the upload is an image
  # Handles the non-processing of non-images and still allows me to have the styles param
  # http://stackoverflow.com/questions/2919811/styles-in-paperclip-only-if-its-an-image-rails
  before_file_post_process :process_only_images
  
  private
  
  def process_only_images
    if !(file.content_type =~ %r{^(image|(x-)?application)/(x-png|pjpeg|jpeg|jpg|png|gif)$})
      return false 
    end
  end
end