Paperclip custom processor not changing image type

问题

I'm having a few problems with a paperclip custom processor.

At the command line this line :

$ convert cats.jpg -thumbnail 300x400  -bordercolor white -background black  +polaroid  cats.png

Successfully converts this :

https://dl.dropboxusercontent.com/u/4233433/cats.jpg

Into this :

https://dl.dropboxusercontent.com/u/4233433/cats.png

i.e a JPEG converted into a PNG with a transparent background. Which is exactly what I am trying to achieve.

However when I attempt to do this within Rails (4.0.1) using Paperclip I end up with :

[Link posted in comment]

It's renamed as a PNG but is actually a JPEG.

My model :

class Submission < ActiveRecord::Base
    has_attached_file :photo,
              processors: [:polarize],
              styles: {
                polarized: {
                  format: 'png',
                  is_polarized: true
                }
              } 

    belongs_to :user
end

And my processor :

module Paperclip
  class Polarize < Processor
    def initialize file, options = {}, attachment = nil
      super
      @file           = file
      @attachment     = attachment
      @is_polarized   = options[:is_polarized]
      @current_format = File.extname(@file.path) 
      @format         = options[:format]
      @basename       = File.basename(@file.path, @current_format)
    end

    def make
      temp_file = Tempfile.new([@basename, @format].compact.join("."))
      temp_file.binmode

      if @is_polarized
        run_string =  "convert #{fromfile} -thumbnail 300x400  -bordercolor white -background white  +polaroid  #{tofile(temp_file)}"    
        Paperclip.run(run_string)
      end

      temp_file
    end

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

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

In my Database photo_content_type is image/jpeg and photo_file_name is cats.jpg when I would have expected image/png and cats.png respectively. Any ideas?

UPDATE

The error was in this line

temp_file = Tempfile.new([@basename, @format].compact.join("."))

changing it to

temp_file = Tempfile.new([@basename, @format])

fixes things. Credit to shaun-frost-duke-jackson

回答1:

Have a look at the documentation on the website but pretty sure it should be like below:

has_attached_file :avatar, :styles => { :thumb => ["32x32#", :png] }

https://github.com/thoughtbot/paperclip

Under post processing

Guess your issue is here:

@format         = options[:format]
@basename       = File.basename(@file.path, @current_format)
temp_file = Tempfile.new([@basename, @format].compact.join("."))

来源：https://stackoverflow.com/questions/20225589/paperclip-custom-processor-not-changing-image-type

标签

ruby-on-rails

ImageMagick

paperclip