Add handling of format change at multi page pdf

File variable can be "filename-*.ext". So later following image manipulations will affect all layers.

lib/image_sorcery.rb

@@ -91,6 +91,10 @@ def replace_file(format)
     File.delete @file
     @file = File.join File.dirname(@file), File.basename(@file, File.extname(@file)) + "." + format
     @filename_changed = true
+
+    unless File.exists? @file
+      @file = File.join File.dirname(@file), File.basename(@file, File.extname(@file)) + "-*." + format
+    end
   end
 
   def convert_to_command(tokens)

spec/image_sorcery_examples_spec.rb

@@ -61,12 +61,22 @@
         end
 
         it "should create file with new extension" do
-          File.exists?("./spec/fixtures/pdf-sample-2.png").should be_true
+
+          case new_instance_method
+            when "new"
+              File.exists?("./spec/fixtures/pdf-sample-2-0.png").should be_true
+              File.exists?("./spec/fixtures/pdf-sample-2-1.png").should be_true
+            when "gm"
+              File.exists?("./spec/fixtures/pdf-sample-2.png").should be_true
+          end
         end
 
         its(:identify) { should include "PNG 595x842" }
 
         its(:filename_changed?) { should be_true }
+
+        its(:file) { should eq "./spec/fixtures/pdf-sample-2.png" } if new_instance_method == "gm"
+        its(:file) { should eq "./spec/fixtures/pdf-sample-2-*.png" } if new_instance_method == "new"
       end
     end
   end