Use a picture format for ticketing

Instead of analyzing image size using the local file, rely on a
processed image of the appropriate dimensions.

Resolves #1828

app/uploaders/picture_uploader.rb

@@ -52,10 +52,6 @@ class PictureUploader < CarrierWave::Uploader::Base
     "system/#{object_class_name}/#{mounted_as}/#{model.id}"
   end
 
-  def image
-    @image ||= MiniMagick::Image.open(file.file)
-  end
-
   # Create different versions of your uploaded files:
   version :large do
     process resize_to_fit: [300, 300]