CarrierWave - PDF - 只选择第一页

Question

我在我的rails应用程序中安装了carrierwave。但是，当用户上传多页PDF时，我只希望应用程序获取文档中的第一页并将其转换为JPEG格式。这是可能的，并用什么命令？

这是我的上传者。

# encoding: utf-8 

class ImageUploader < CarrierWave::Uploader::Base 

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

    # Include the Sprockets helpers for Rails 3.1+ asset pipeline compatibility: 
    include Sprockets::Helpers::RailsHelper 
    include Sprockets::Helpers::IsolatedHelper 

    # Choose what kind of storage to use for this uploader: 
    storage :file 
    # storage :fog 

    # Override the directory where uploaded files will be stored. 
    # This is a sensible default for uploaders that are meant to be mounted: 
    def store_dir 
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}" 
    end 

    # Provide a default URL as a default if there hasn't been a file uploaded: 
    # def default_url 
    # # For Rails 3.1+ asset pipeline compatibility: 
    # # asset_path("fallback/" + [version_name, "default.png"].compact.join('_')) 
    # 
    # "/images/fallback/" + [version_name, "default.png"].compact.join('_') 
    # end 

    # Process files as they are uploaded: 
    # process :scale => [200, 300] 
    # 
    # def scale(width, height) 
    # # do something 
    # end 
    # Create different versions of your uploaded files: 
    version :thumb do 
    process :resize_to_fill => [150, 210] 
    process :convert => :jpg 

    def full_filename (for_file = model.source.file) 
     super.chomp(File.extname(super)) + '.jpg' 
    end 
    end 

    version :thumb_big do 
    process :resize_to_fill => [320, 440] 
    process :convert => :jpg 

    def full_filename (for_file = model.source.file) 
     super.chomp(File.extname(super)) + '.jpg' 
    end 
    end 

    version :normal do 
    process :resize_to_fill => [450, 630] 
    process :convert => :jpg 

    def full_filename (for_file = model.source.file) 
     super.chomp(File.extname(super)) + '.jpg' 
    end 
    end 

    # Add a white list of extensions which are allowed to be uploaded. 
    # For images you might use something like this: 
    # def extension_white_list 
    # %w(jpg jpeg gif png) 
    # end 

    # Override the filename of the uploaded files: 
    # Avoid using model.id or version_name here, see uploader/store.rb for details. 
    # def filename 
    # "something.jpg" if original_filename 
    # end 

end 

Answer 1

我觉得这对你的作品：

read more

def cover 
    manipulate! do |frame, index| 
     frame if index.zero? 
    end 
    end 


version :thumb do 
    process :cover 
    process :resize_to_fill => [150, 210] 
    process :convert => :jpg 

    def full_filename (for_file = model.source.file) 
     super.chomp(File.extname(super)) + '.jpg' 
    end 
    end 

version :thumb_big do 
    process :cover 
    process :resize_to_fill => [320, 440] 
    process :convert => :jpg 

    def full_filename (for_file = model.source.file) 
    super.chomp(File.extname(super)) + '.jpg' 
    end 
end 

version :normal do 
    process :cover 
    process :resize_to_fill => [450, 630] 
    process :convert => :jpg 

    def full_filename (for_file = model.source.file) 
    super.chomp(File.extname(super)) + '.jpg' 
    end 
end