Enable progressive encoding for new JPEG thumbnails and samples; see issue #1665

Enable progressive encoding for resized images, as discussed in issue #1665. Works with every normal browser, but might introduce compatibility issues with certain embedded devices.

lib/danbooru_image_resizer/danbooru_image_resizer.rb

@@ -18,6 +18,8 @@ module Danbooru
 
     image.write(write_path) do
       self.quality = resize_quality
+      # setting PlaneInterlace enables progressive encoding for JPEGs
+      self.interlace = Magick::PlaneInterlace
     end
 
     image.destroy!