share image info cache between primary and scratch documents to avoid decoding same image more than once (PR #2321)

2 files changed, 29 insertions, 0 deletions

diff --git a/lib/asciidoctor/pdf/converter.rb b/lib/asciidoctor/pdf/converter.rb
index 576c8682..f00441f0 100644
--- a/lib/asciidoctor/pdf/converter.rb
+++ b/lib/asciidoctor/pdf/converter.rb
@@ -432,6 +432,7 @@ module Asciidoctor
         else
           @optimize = nil
         end
+        image_info_cache
         # allocate_scratch_prototype calls create_scrate_prototype to set up the scratch prototype
         # scratch calls init_scratch on a copy of the prototype to instantiate a scratch document
         # push_scratch and pop_scratch make changes to the document catalog and attributes transactional
@@ -5212,6 +5213,7 @@ module Asciidoctor
           # NOTE: prepare scratch document to use page margin from recto side (which has same width as verso side)
           set_page_margin page_margin_recto
         end
+        @image_info_cache = originator.instance_variable_get :@image_info_cache
         @scratch_prototype = originator.instance_variable_get :@scratch_prototype
         @tmp_files = originator.instance_variable_get :@tmp_files
         text_formatter.scratch = true
diff --git a/lib/asciidoctor/pdf/ext/prawn/images.rb b/lib/asciidoctor/pdf/ext/prawn/images.rb
index 7f85d431..414ae4e9 100644
--- a/lib/asciidoctor/pdf/ext/prawn/images.rb
+++ b/lib/asciidoctor/pdf/ext/prawn/images.rb
@@ -33,9 +33,36 @@ module Asciidoctor
         end
       end
 
+      # Override built-in method to cache info separately from obj.
+      def build_image_object file
+        if ::File === file
+          cache_key = ((::File.absolute_path? (file_path = file.path)) ? file_path : (File.absolute_path file_path)).to_sym
+          info = image_info_cache[cache_key]
+        end
+        unless info
+          image_content = verify_and_read_image file
+          if cache_key || !(info = image_info_cache[(cache_key = ::Digest::SHA1.hexdigest image_content)])
+            # build the image object
+            info = (::Prawn.image_handler.find image_content).new image_content
+            renderer.min_version info.min_pdf_version if info.respond_to? :min_pdf_version
+            image_info_cache[cache_key] = info
+          end
+        end
+        # reuse image if it has already been embedded
+        unless (image_obj = image_registry[cache_key])
+          # add the image to the PDF then register it in case we see it again
+          image_registry[cache_key] = image_obj = info.build_pdf_object self
+        end
+        [image_obj, info]
+      end
+
       def recommend_prawn_gmagick? err, image_format
         ::Prawn::Errors::UnsupportedImageType === err && !(defined? ::GMagick::Image) && ((err.message.include? 'PNG') || (%w(jpg png).none? image_format))
       end
+
+      def image_info_cache
+        @image_info_cache ||= {}
+      end
     end
 
     ::Prawn::Document.extensions << Images