ruby-on-rails-3 - 回形针后期处理 - 如何使用 jpegoptim/optpng 压缩图像

Question

我想用 jpegoptim或 optipng压缩用户通过 Paperclip 上传的图像。

我有一个回形针模型配置为:

  has_attached_file :image,
                    :styles => {:thumb => '50x50>', :preview => '270x270>' },
                    :url => "/system/:class/:attachment/:id/:basename_:style.:extension",
                    :path => ":rails_root/public/system/:class/:attachment/:id/:basename_:style.:extension"

问题 1:
是否可以压缩用户上传的原始图像，然后让Paperclip调整它的大小，这样只有一个压缩过程？以及怎么做？

问题 2:
我将通过 after_post_process 来做这件事回调，我可以从 image.queued_for_write 获取三个文件的所有实例我想通过文件扩展名触发 jpegoptim/optipng，但是当我使用 current_format = File.extname(file.path) 时，我得到类似的信息:.jpg20120508-7991-cqcpf2 .是否可以获取扩展字符串 jpg ?或者我只是检查扩展字符串是否包含在该字符串中是否安全？

Answer 1

由于没有其他答案，以下是我在我的项目中的做法，而且它似乎可以正常工作几个月。

class AttachedImage < ActiveRecord::Base
  belongs_to :attachable, :polymorphic => true

  validates_attachment_presence :image
  validates_attachment_content_type :image, :content_type=>['image/jpeg', 'image/png', 'image/gif']

  has_attached_file :image,
                    :styles => {:thumb => '50x50>', :preview => '270x270>' },
                    # :processors => [:image_compressor],
                    :url => "/system/:class/:attachment/:id/:basename_:style.:extension",
                    :path => ":rails_root/public/system/:class/:attachment/:id/:basename_:style.:extension"


  after_post_process :compress

  private
  def compress
    current_format = File.extname(image.queued_for_write[:original].path)

    image.queued_for_write.each do |key, file|
      reg_jpegoptim = /(jpg|jpeg|jfif)/i
      reg_optipng = /(png|bmp|gif|pnm|tiff)/i

      logger.info("Processing compression: key: #{key} - file: #{file.path} - ext: #{current_format}")

      if current_format =~ reg_jpegoptim
        compress_with_jpegoptim(file)
      elsif current_format =~ reg_optipng
        compress_with_optpng(file)
      else
        logger.info("File: #{file.path} is not compressed!")
      end
    end
  end

  def compress_with_jpegoptim(file)
    current_size = File.size(file.path)
    Paperclip.run("jpegoptim", "-o --strip-all #{file.path}")
    compressed_size = File.size(file.path)
    compressed_ratio = (current_size - compressed_size) / current_size.to_f
    logger.debug("#{current_size} - #{compressed_size} - #{compressed_ratio}")
    logger.debug("JPEG family compressed, compressed: #{ '%.2f' % (compressed_ratio * 100) }%")
  end

  def compress_with_optpng(file)
    current_size = File.size(file.path)
    Paperclip.run("optipng", "-o7 --strip=all #{file.path}")
    compressed_size = File.size(file.path)
    compressed_ratio = (current_size - compressed_size) / current_size.to_f
    logger.debug("#{current_size} - #{compressed_size} - #{compressed_ratio}")
    logger.debug("PNG family compressed, compressed: #{ '%.2f' % (compressed_ratio * 100) }%")   
  end                              
end