rely on preview urls if available for gallery

app/logical/sources/strategies/base.rb

@@ -53,6 +53,16 @@ module Sources
         image_urls.first
       end
 
+      # A smaller representation of the image that's suitable for
+      # displaying previews.
+      def preview_urls
+        image_urls
+      end
+
+      def preview_url
+        preview_urls.first
+      end
+
       # Whatever <tt>url</tt> is, this method should return a link to the HTML
       # page containing the resource. It should not be a binary file. It will
       # eventually be assigned as the source for the post, but it does not

app/logical/sources/strategies/pixiv.rb

@@ -50,6 +50,12 @@ module Sources
         [url]
       end
 
+      def preview_urls
+        image_urls.map do |x|
+          x.sub(%r!pximg\.net/img-original/img!, "pximg.net/c/240x240/img-master/img")
+        end
+      end
+
       def page_url
         if novel_id.present?
           return "https://www.pixiv.net/novel/show.php?id=#{novel_id}&mode=cover"

app/logical/sources/strategies/tumblr.rb

@@ -36,6 +36,12 @@ module Sources::Strategies
         .uniq
     end
 
+    def preview_urls
+      image_urls.map do |x|
+        x.sub(%r!_1280\.(jpg|png|gif|jpeg)\z!, '_250.\1')
+      end
+    end
+
     def page_url
       [url, referer_url].each do |x|
         if x =~ POST

app/logical/sources/strategies/twitter.rb

@@ -36,6 +36,12 @@ module Sources::Strategies
     end
     memoize :image_urls
 
+    def preview_urls
+      image_urls.map do |x|
+        x.sub(%r!\.(jpg|jpeg|png|gif)(?::orig)?\z!i, '.\1:small')
+      end
+    end
+
     def page_url
       [url, referer_url].each do |x|
         if self.class.status_id_from_url(x).present?

app/views/uploads/batch.html.erb

@@ -9,7 +9,7 @@
 
     <% if @source.present? %>
       <section>
-        <% @source.image_urls.each.with_index do |url, i| %>
+        <% @source.image_urls.zip(@source.preview_urls).each.with_index do |(url, preview_url), i| %>
           <div class="upload-preview">
             <p class="caption-top">
               <%= link_to "Image ##{i}", new_upload_path(url: url, ref: @url), target: "_blank" %>
@@ -17,7 +17,7 @@
 
             <%= link_to new_upload_path(url: url, ref: @url), target: "_blank" do %>
               <% if ImageProxy.needs_proxy?(url) %>
-                <%= image_tag(image_proxy_uploads_path(url: url)) %>
+                <%= image_tag(image_proxy_uploads_path(url: preview_url)) %>
               <% elsif url.is_a?(String) %>
                 <%= image_tag url %>
               <% else %>

test/unit/sources/pixiv_test.rb

@@ -102,6 +102,10 @@ module Sources
           assert_equal("https://i.pximg.net/img-original/img/2017/11/21/05/12/37/65981735_p0.jpg", @site.image_url)
         end
 
+        should "get the preview size image url" do
+          assert_equal("https://i.pximg.net/c/240x240/img-master/img/2017/11/21/05/12/37/65981735_p0.jpg", @site.preview_url)          
+        end
+
         should "get the page count" do
           assert_equal(1, @site.image_urls.size)
         end

test/unit/sources/tumblr_test.rb

@@ -70,6 +70,10 @@ module Sources
         assert_equal("https://media.tumblr.com/3bbfcbf075ddf969c996641b264086fd/tumblr_os2buiIOt51wsfqepo1_1280.png", @site.image_url)
       end
 
+      should "get the preview url" do
+        assert_equal("https://media.tumblr.com/3bbfcbf075ddf969c996641b264086fd/tumblr_os2buiIOt51wsfqepo1_250.png", @site.preview_url)
+      end
+
       should "get the artist" do
         CurrentUser.user = FactoryBot.create(:user)
         CurrentUser.ip_addr = "127.0.0.1"

test/unit/sources/twitter_test.rb

@@ -78,6 +78,10 @@ module Sources
         assert_equal("https://pbs.twimg.com/media/C1kt72yVEAEGpOv.jpg:orig", @site.image_url)
       end
 
+      should "get the preview url" do
+        assert_equal("https://pbs.twimg.com/media/C1kt72yVEAEGpOv.jpg:small", @site.preview_url)
+      end
+
       should "get the canonical url" do
         assert_equal("https://twitter.com/aranobu/status/817736083567820800", @site.canonical_url)
       end