RMagick mask回形針圖像附件

Question

我使用回形針將圖像文件附加到對象，一切都很好，但我還想在上載時掩蓋（最好只有一種圖像樣式 - main_feature）圖像。我可以使用masked_image.write('result.png')保存我的蒙版圖像，但似乎無法讓它更新Paperclip的圖像屬性。用下面的代碼我得到這個錯誤：

No handler found for /var/folders/q1/xf59whv514lgw_xr10hb208m0000gn/T/gaither-nomask20130312-80235-yaj1s7.png PNG 1020x470 1020x470+0+0 DirectClass 8-bit 

has_attached_file :image, 
    :styles =>{ 
    :main_feature => "1020x470", 
    :top_feature => "345x159", 
    :smallest => "229x131" 
}, 
:storage => :s3, 
:s3_credentials => "#{Rails.root}/config/s3.yml", 
:path => ":attachment/:id/:style.:extension", 
:url => "/:id/:style/:basename.:extension", 
:bucket => "bucketname" 

after_image_post_process :post_process_image 

def post_process_image 
    require 'rubygems' 
    require 'RMagick' 
    require "open-uri" 


    mask = Magick::ImageList.new 
    urlimage = open("http://bucket.s3.amazonaws.com/mask.png") 
    mask.from_blob(urlimage.read) 

    imgfile = Magick::Image.read(image.queued_for_write[:original].path).first 

    mask.matte = true 
    imgfile.matte = true 


    masked_image = imgfile.composite(mask, Magick::CenterGravity, Magick::CopyOpacityCompositeOp) 
    self.update_attribute(:image, masked_image) 

end 

Answer 1

一個小試驗和錯誤之後，我最後寫一個回形針處理器：

型號：

:styles =>{ 
    :main_feature => {:geometry => "1020x470", :processors => [:masker] }, 
    :top_feature => "345x159", 
    :smallest => "229x131" 
} 

/lib/paperclip_processors/masker.rb：

module Paperclip 
class Masker < Processor 
    def initialize file, options = {}, attachment = nil 
    super 
    @format = File.extname(@file.path) 
    @basename = File.basename(@file.path, @format) 
    end 

def make 

    src = @file 
    dst = Tempfile.new([@basename, @format]) 
    dst.binmode 

    begin 
    parameters = [] 

    parameters << ':source' 
    parameters << ':mask' 
    parameters << '-alpha' 
    parameters << 'on' 
    parameters << '-compose' 
    parameters << 'CopyOpacity' 
    parameters << '-composite' 
    parameters << ':dest' 

    parameters = parameters.flatten.compact.join(" ").strip.squeeze(" ") 

    mask_path = File.expand_path('lib/paperclip_processors/mask.png') 
    success = Paperclip.run("convert", parameters, :source => "#{File.expand_path(src.path)}[0]", :mask => "#{mask_path}[0]", :dest => File.expand_path(dst.path)) 



    rescue PaperclipCommandLineError => e 
     raise PaperclipError, "There was an error during the mask for #{@basename}" if @whiny 
    end 

    dst 
    end 

    end 
end