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/pdfs/ticket_pdf.rb

@@ -1,3 +1,5 @@
+require 'open-uri'
+
 class TicketPdf < Prawn::Document
   def initialize(conference, user, physical_ticket, ticket_layout, file_name)
     super(page_layout: ticket_layout, page_size: 'A4', filename: file_name)
@@ -43,11 +45,17 @@ class TicketPdf < Prawn::Document
   def draw_second_square
     move_up 150
     if @conference.picture?
-      if 7 * @conference.picture.image[:width] > 12 * @conference.picture.image[:height]
-        image "#{Rails.root}/public#{@conference.picture_url}", at: [@mid_horizontal + 30, cursor], width: 120
-      else
-        image "#{Rails.root}/public#{@conference.picture_url}", at: [@mid_horizontal + 30, cursor], height: 70
-      end
+      conference_image = case @conference.picture.ticket.url[0, 4]
+                         when 'http', 'ftp:' # CDNs
+                           open(@conference.picture.ticket.url)
+                         when '/sys' # local storage
+                           open([
+                             Rails.root,
+                             '/public',
+                             @conference.picture.ticket.url
+                           ].join)
+                         end
+      image conference_image, at: [@mid_horizontal + 30, cursor]
     else
       image "#{Rails.root}/public/img/osem-logo.png", at: [@mid_horizontal + 30, cursor], height: 70
     end

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]

app/views/physical_tickets/show.html.haml

@@ -31,12 +31,7 @@
         = @user.email
     .col-md-5.col-md-offset-2.box.well
       - if @conference.picture?
-        - width = @conference.picture.image[:width]
-        - height = @conference.picture.image[:height]
-        - if 10 * width > 15 * height
-          = image_tag(@conference.picture_url, width: '150')
-        - else
-          = image_tag(@conference.picture_url, height: '100')
+        = image_tag(@conference.picture.ticket.url, class: 'img-responsive')
       - else
         = image_tag('/img/osem-logo.png', class: 'img-responsive')
       %p.text-left