redmine_thumbnails cache

$ git diff
diff --git a/init.rb b/init.rb
index f0a5316..29f7a2d 100644
--- a/init.rb
+++ b/init.rb
@@ -73,6 +73,14 @@ Redmine::WikiFormatting::Macros.register do
                           :id => attach.id,
                           :filename => attach.filename
 
+    thumb_filename = "#{tw}_#{th}_#{attach.disk_filename}"
+    unless File.exists? "public/thumbs/#{thumb_filename}"
+      image.resize "#{tw}x#{th}"
+      FileUtils.mkdir("public/thumbs") unless File.exists? "public/thumbs"
+      image.write("public/thumbs/#{thumb_filename}")
+    end
+    thumb_link = "/thumbs/#{thumb_filename}"
+
     if ((tw == 0 || image[:width] < tw) && (th == 0 || image[:height] < th))
       html = <<-eos
 <img src="#{attach_link}" />