image thumbnails, catch crashy sites with screenshots

workers/thumbnail_worker.rb

@@ -0,0 +1,28 @@
+require 'RMagick'
+
+class ThumbnailWorker
+  REQUIRED_RESOLUTIONS = ['105x63']
+  THUMBNAILS_PATH = File.join DIR_ROOT, 'public', 'site_thumbnails'
+  include Sidekiq::Worker
+  sidekiq_options queue: :thumbnails, retry: 3, backtrace: true
+
+  def perform(username, filename)
+    img_list = Magick::ImageList.new
+    img_list.from_blob File.read(File.join(Site::SITE_FILES_ROOT, username, filename))
+    img = img_list.first
+
+    user_thumbnails_path = File.join THUMBNAILS_PATH, username
+    FileUtils.mkdir_p user_thumbnails_path
+
+    REQUIRED_RESOLUTIONS.each do |res|
+      resimg = img.resize_to_fit(*res.split('x').collect {|r| r.to_i})
+      format = File.extname(filename).gsub('.', '')
+
+      save_ext = format.match(Site::LOSSY_IMAGE_REGEX) ? 'jpg' : 'png'
+
+      resimg.write(File.join(user_thumbnails_path, "#{filename}.#{res}.#{save_ext}")) {
+        self.quality = 90
+      }
+    end
+  end
+end