discourse/app/models/optimized_image.rb

require "digest/sha1"

class OptimizedImage < ActiveRecord::Base
  belongs_to :upload

  def self.create_for(upload, width, height)
    return unless width && height

    @image_sorcery_loaded ||= require "image_sorcery"

    external_copy = Discourse.store.download(upload) if Discourse.store.external?
    original_path = if Discourse.store.external?
      external_copy.path
    else
      Discourse.store.path_for(upload)
    end

    # create a temp file with the same extension as the original
    temp_file = Tempfile.new(["discourse-thumbnail", File.extname(original_path)])
    temp_path = temp_file.path

    if ImageSorcery.new(original_path).convert(temp_path, resize: "#{width}x#{height}")
      thumbnail = OptimizedImage.create!(
        upload_id: upload.id,
        sha1: Digest::SHA1.file(temp_path).hexdigest,
        extension: File.extname(temp_path),
        width: width,
        height: height,
        url: "",
      )
      # store the optimized image and update its url
      thumbnail.url = Discourse.store.store_optimized_image(temp_file, thumbnail)
      thumbnail.save
    end

    # close && remove temp file
    temp_file.close!
    # make sure we remove the cached copy from external stores
    external_copy.close! if Discourse.store.external?

    thumbnail
  end

  def destroy
    OptimizedImage.transaction do
      Discourse.store.remove_optimized_image(self)
      super
    end
  end

end

# == Schema Information
#
# Table name: optimized_images
#
#  id        :integer          not null, primary key
#  sha1      :string(40)       not null
#  extension :string(10)       not null
#  width     :integer          not null
#  height    :integer          not null
#  upload_id :integer          not null
#  url       :string(255)      not null
#
# Indexes
#
#  index_optimized_images_on_upload_id                       (upload_id)
#  index_optimized_images_on_upload_id_and_width_and_height  (upload_id,width,height) UNIQUE
#