Merge pull request #1988 from samvera/blank_tif_bug

make sure layers are flattened to fix pdf tripple issue

lib/hydra/derivatives/processors/image_decorator.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+# Fix PDF tripple issue
+
+module Hydra
+  module Derivatives
+    module Processors
+      module ImageDecorator
+        protected
+
+          # When resizing images, it is necessary to flatten any layers, otherwise the background
+          # may be completely black. This happens especially with PDFs. See https://github.com/samvera/hydra-derivatives/issues/110
+          def create_resized_image
+            create_image do |xfrm|
+              if size
+                xfrm.combine_options do |i|
+                  i.flatten
+                  i.resize(size)
+                end
+              end
+            end
+          end
+      end
+    end
+  end
+end
+
+::Hydra::Derivatives::Processors::Image.prepend(Hydra::Derivatives::Processors::ImageDecorator)