dragonfly.rb

require 'dragonfly'

# Adding image_optim to Dragonfly
image_optim = ImageOptim.new(nice: 20, threads: 4, verbose: true, advpng: { level: 4 }, jpegoptim: { strip: :all }, jpegrecompress: { quality: 2 }, optipng: { level: 4 }, pngcrush:{ chunks: :alla } )

# Configure
Dragonfly.app.configure do
  plugin :imagemagick
  
  # Image optimization processor.
  processor :image_optim do |content, *args|
    optimized = image_optim.optimize_image_data(content.data)
    content.update(optimized) if optimized
    puts "********************************"
    puts "optimized"
    puts "****************************"
  end

.
.
.
.

image.rb

class Image < ActiveRecord::Base
  include Concerns::Utils

  belongs_to :user

  dragonfly_accessor :asset do
    after_assign {|img| self.asset = img.image_optim }
    storage_options do |attachment|
      { headers: {"x-amz-acl" => "public-read-write"} }
    end
  end
  abs_url_for :asset
end