如何使用Paperclip仅为图像文件创建缩略图？

Question

我使用以下代码Asset从上传的文件中创建s:

def upload
  uploader = User.find_by_id(params[:uploader_id])
  params[:assets].each do |file|
    new_asset = uploader.assets.build(:asset => file) # Here the error appears
    new_asset.save
  end
  ...
end

我注意到,当我上传非图像文件时,例如my.xlsx,我收到以下错误:

[paperclip] identify -format %wx%h "C:/temp/stream20110628-460-3vqjnd.xlsx[0]" 2>NUL
[paperclip] An error was received while processing: 
#<Paperclip::NotIdentifiedByImageMagickError: C:/temp/stream20110628-460-3vqjnd.xlsx is
not recognized by the 'identify' command.>

(对于图像文件,一切正常:创建缩略图,没有错误.)

那是因为Paperclip试图从中创建缩略图my.xlsx吗？

什么配置只为图像文件创建缩略图？

这是一些相关的代码:

class Asset < ActiveRecord::Base
  belongs_to :uploader, :class_name => "User"
  has_attached_file :asset, :styles => { :thumb => "80x80#" }
end

Answer 1

我用了以下很好的解决方案:

before_post_process :image?

def image?
  (asset_content_type =~ SUPPORTED_IMAGES_REGEX).present?
end

哪里:

SUPPORTED_IMAGE_FORMATS = ["image/jpeg", "image/png", "image/gif", "image/bmp"]
SUPPORTED_IMAGES_REGEX = Regexp.new('\A(' + SUPPORTED_IMAGE_FORMATS.join('|') + ')\Z')