如何使用Rails3生成文件的缩略图？

Question

我想获取word和pdf文件的缩略图（文件内容的预览），我使用carrierwave来处理上传。

我按照以下方式配置上传器：

# encoding: utf-8
require 'carrierwave/processing/mime_types'

class FileUploader < CarrierWave::Uploader::Base

  # Include RMagick or ImageScience support:
  # include CarrierWave::RMagick
  include CarrierWave::MiniMagick
  # include CarrierWave::ImageScience

  include CarrierWave::MimeTypes

  version :m do
    process :resize_to_fill => [75, 75]
  end

  version :b do
    process :resize_to_fill => [125, 125]
  end
  ....

end

但它不能用于非图像