如何使用Imagemagick给图片添加水印？

Question

我想加上这句话，因为我花了很长时间才让它正常工作，我看到很多人在使用时遇到了问题。

我试图在Spree（Rails）应用程序的图像模型中添加一个水印处理器。但是，我一直收到以下错误信息：

"无法处理流的水印"

"合成：无法打开图像"

"错误/ blob.c / OpenBlob / 2588：没有那个文件或目录"

"@ error / png.c / ReadPNGImage / 3633"

"PaperclipCommandNotFoundError"

"PaperclipCommandLineError"

- Chris Edwards

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虽然你想分享这些信息很好，但StackOverflow是一个“问答”网站。你应该重新格式化你的帖子，只包含问题，并将解决方案作为答案发布（然后你可以接受它）。 - Chowlett

等待期结束后，我本来就要这样做的，但同时我想发布完整的解决方案，以免浪费人们尝试解决问题的时间 :) - Chris Edwards

啊，好的。我忘记了有一段时间你不能回答自己的问题。那就做得好！ - Chowlett

Answer 1

我在RAILS_ROOT/lib/paperclip_processors/watermark.rb中添加了以下内容：

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

        command = "convert"
        params = [fromfile]
        params += transformation_command
        params << tofile(dst)
        begin
          success = Paperclip.run(command, params.flatten.compact.collect{|e| "'#{e}'"}.join(" "))
        rescue PaperclipCommandLineError
          raise PaperclipError, "There was an error resizing and cropping #{@basename}" if @whiny
        end

        if watermark_path
          command = "composite"
          params = %W[-gravity #{@position} #{watermark_path} #{tofile(dst)}]
          params << tofile(dst)
          begin
            success = Paperclip.run(command, params.flatten.compact.collect{|e| "'#{e}'"}.join(" "))
          rescue PaperclipCommandLineError
            raise PaperclipError, "There was an error processing the watermark for #{@basename}" if @whiny
          end
        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

更新： 如果您正在使用新版的Paperclip（3+），则开始块现在应该如下所示：

begin
  Paperclip.run(command, params.join(' '))
rescue Cocaine::ExitStatusError => e
  raise Paperclip::Error, "There was an error processing the watermark for #{@basename}" if @whiny
rescue Cocaine::CommandNotFoundError => e
  raise Paperclip::Errors::CommandNotFoundError.new("Could not run the `convert` command. Please install ImageMagick.")
end

然后是 image_decorator.rb 模型:

require 'paperclip_processors/watermark'

Spree::Image.class_eval do

  has_attached_file :attachment,
                    :processors => [:thumbnail, :watermark],
                    :styles => { :mini => '48x48>', :small => '100x100>', :product => '160x160#',
                      :large => {
                        :geometry => '460x680>',
                        :watermark_path => "#{Rails.root}/public/spree/watermark.png",
                        :position => 'SouthWest',
                        :format => :png
                      }
                    },
                    :default_style => :product,
                    :url => '/spree/products/:id/:style/:basename.:extension',
                    :path => ':rails_root/public/spree/products/:id/:style/:basename.:extension'

end

- Chris Edwards

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这是一个答案还是问题的一部分？ - Ryan Bigg