如何使用Imagemagick为图像添加水印？
我以为我会加上这个，因为我花了很多时间才开始工作，我看到很多人都遇到了问题。
我正在尝试在Spree（Rails）应用程序中为图像模型添加水印处理器。 我收到的错误如下：
There was an error processing the watermark for stream
composite: unable to open image
No such file or directory @ error/blob.c/OpenBlob/2588
@ error/png.c/ReadPNGImage/3633
PaperclipCommandNotFoundError
PaperclipCommandLineError
我在RAILS_ROOT/lib/paperclip_processors/watermark.rb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：如果您使用的是新版本的回形针（3+），那么begin块现在应如下所示：
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