Add blurhash to preview cards (#13984)

Fixes #13001

app/models/preview_card.rb

@@ -23,19 +23,25 @@
 #  updated_at                   :datetime         not null
 #  embed_url                    :string           default(""), not null
 #  image_storage_schema_version :integer
+#  blurhash                     :string
 #
 
 class PreviewCard < ApplicationRecord
   IMAGE_MIME_TYPES = ['image/jpeg', 'image/png', 'image/gif'].freeze
   LIMIT = 1.megabytes
 
+  BLURHASH_OPTIONS = {
+    x_comp: 4,
+    y_comp: 4,
+  }.freeze
+
   self.inheritance_column = false
 
   enum type: [:link, :photo, :video, :rich]
 
   has_and_belongs_to_many :statuses
 
-  has_attached_file :image, styles: ->(f) { image_styles(f) }, convert_options: { all: '-quality 80 -strip' }
+  has_attached_file :image, processors: [:thumbnail, :blurhash_transcoder], styles: ->(f) { image_styles(f) }, convert_options: { all: '-quality 80 -strip' }
 
   include Attachmentable
 
@@ -72,6 +78,7 @@ class PreviewCard < ApplicationRecord
           geometry: '400x400>',
           file_geometry_parser: FastGeometryParser,
           convert_options: '-coalesce -strip',
+          blurhash: BLURHASH_OPTIONS,
         },
       }
 

app/serializers/rest/preview_card_serializer.rb

@@ -6,7 +6,7 @@ class REST::PreviewCardSerializer < ActiveModel::Serializer
   attributes :url, :title, :description, :type,
              :author_name, :author_url, :provider_name,
              :provider_url, :html, :width, :height,
-             :image, :embed_url
+             :image, :embed_url, :blurhash
 
   def image
     object.image? ? full_asset_url(object.image.url(:original)) : nil

db/migrate/20200605155027_add_blurhash_to_preview_cards.rb

@@ -0,0 +1,5 @@
+class AddBlurhashToPreviewCards < ActiveRecord::Migration[5.2]
+  def change
+    add_column :preview_cards, :blurhash, :string
+  end
+end

db/schema.rb

@@ -10,8 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_06_01_222558) do
-
+ActiveRecord::Schema.define(version: 2020_06_05_155027) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -648,6 +647,7 @@ ActiveRecord::Schema.define(version: 2020_06_01_222558) do
     t.datetime "updated_at", null: false
     t.string "embed_url", default: "", null: false
     t.integer "image_storage_schema_version"
+    t.string "blurhash"
     t.index ["url"], name: "index_preview_cards_on_url", unique: true
   end
 

lib/paperclip/blurhash_transcoder.rb

@@ -3,7 +3,7 @@
 module Paperclip
   class BlurhashTranscoder < Paperclip::Processor
     def make
-      return @file unless options[:style] == :small
+      return @file unless options[:style] == :small || options[:blurhash]
 
       pixels   = convert(':source RGB:-', source: File.expand_path(@file.path)).unpack('C*')
       geometry = options.fetch(:file_geometry_parser).from_file(@file)