ruby-on-rails – 使用回形针,导轨4的水印图像

Watermark.rb：

module Paperclip
  class Watermark < Processor
    # Handles watermarking of images that are uploaded.
    attr_accessor :current_geometry,:target_geometry,:format,:whiny,:convert_options,:watermark_path,:watermark_offset,:overlay,:position

    def initialize file,options = {},attachment = nil
      super
      geometry = options[:geometry]
      @file = file
      @crop = geometry[-1,1] == '#'
      @target_geometry = Geometry.parse geometry
      @current_geometry = Geometry.from_file @file
      @convert_options = options[:convert_options]
      @whiny = options[:whiny].nil? ? true : options[:whiny]
      @format = options[:format]
      @watermark_path = options[:watermark_path]
      @position = options[:position].nil? ? "SouthEast" : options[:position]
      @watermark_offset = options[:watermark_offset]
      @overlay = options[:overlay].nil? ? true : false
      @current_format = File.extname(@file.path)
      @basename = File.basename(@file.path,@current_format)
    end

    # TODO: extend watermark

    # Returns true if the +target_geometry+ is meant to crop.
    def crop?
      @crop
    end

    # Returns true if the image is meant to make use of additional convert options.
    def convert_options?
      not @convert_options.blank?
    end

    # Performs the conversion of the +file+ into a watermark. Returns the Tempfile
    # that contains the new image.
    def make
      dst = Tempfile.new([@basename,@format].compact.join("."))
      dst.binmode

      if watermark_path
        command = "composite"
        params = %W[-gravity #{@position}]
        params += %W[-geometry '#{@watermark_offset}'] if @watermark_offset
        params += %W['#{watermark_path}' '#{fromfile}']
        params += transformation_command
        params << "'#{tofile(dst)}'"
      else
        command = "convert"
        params = ["'#{fromfile}'"]
        params += transformation_command
        params << "'#{tofile(dst)}'"
      end

      begin
        Paperclip.run(command,params.join(' '))
      rescue ArgumentError,Cocaine::CommandLineError
        raise PaperclipError,"There was an error processing the watermark for #{@basename}" if @whiny
      end

      dst
    end

    def fromfile
      File.expand_path(@file.path)
    end

    def tofile(destination)
      File.expand_path(destination.path)
    end

    def transformation_command
      scale,crop = @current_geometry.transformation_to(@target_geometry,crop?)
      trans = %W[-resize '#{scale}']
      trans += %W[-crop '#{crop}' +repage] if crop
      trans << convert_options if convert_options?
      trans
    end
  end
end

和型号代码：

has_attached_file :image,:processors => [:watermark],:styles => { 
                    :large => "640x480",:thumb => "100x100",:medium => "300x300",:content => {
                            :geometry => '150x153',:watermark_path => Rails.root.join('app/assets/images/watermark.jpg'),:position => 'SouthWest'
                        },},dependent: :allow_destroy

我试图更新它以使用Rails 4(将attr_accessor移动到模型中的params),但我收到错误：

uninitialized constant Paperclip::Watermark::PaperclipError

有关如何在rails 4 app中实现水印的任何提示？

更新：我能够通过以下更改Graeme的建议来解决未初始化的常量错误：

raise PaperclipError,"There was an error processing the watermark for #{@basename}" if @whiny

至：

raise Paperclip::Error.new("There was an error processing the watermark for #{@basename}") if @whiny

我还必须从模型中删除以下内容才能进行上传处理：

:url => "/images/:style/:id_:style.:extension",:path => ":rails_root/app/assets/images/:style/:id_:style.:extension"

我不明白目的是什么：url和：path在这种情况下,当用户上传图片时？

问题是,即使现在上传了图像,也没有显示水印.思考？

更新2：
为了正确显示水印,我不得不将模型更改为：

has_attached_file :image,:url => "/system/:class/:attachment/:id_partition/:style/:filename",:path => ":rails_root/public/system/:class/:attachment/:id_partition/:style/:filename",:styles => { 
    :large => "640x480",:medium => { 
            :processors => [:watermark],:geometry => '300x300',:watermark_path => Rails.root.join('app/assets/images/icon.gif'),:position => 'SouthWest'
        },dependent: :allow_destroy

关键是删除：content => .唯一剩下的问题是水印正在按比例放大以适应图像的整个宽度.有关如何停止水印缩放的任何建议？