discourse/lib/tasks/images.rake

task "images:compress" => :environment do
  io = ImageOptim.new
  images = Dir.glob("#{Rails.root}/app/**/*.png")
  image_sizes = Hash[*images.map{|i| [i,File.size(i)]}.to_a.flatten]
  io.optimize_images!(images) do |name, optimized|
    if optimized
      new_size = File.size(name)
      puts "#{name} => from: #{image_sizes[name.to_s]} to: #{new_size}"
    end
  end
end

desc "clean orphan uploaded files"
task "images:clean_orphans" => :environment do
  RailsMultisite::ConnectionManagement.each_connection do |db|
    puts "Cleaning up #{db}"
    # ligthweight safety net to prevent users from wiping all their uploads out
    if PostUpload.count == 0 && Upload.count > 0
      puts "The reverse index is empty. Make sure you run the `images:reindex` task"
      next
    end
    Upload.joins("LEFT OUTER JOIN post_uploads ON uploads.id = post_uploads.upload_id")
          .where("post_uploads.upload_id IS NULL")
          .find_each do |u|
      u.destroy
      putc "."
    end
  end
  puts "\ndone."
end