IPhoto Librarys

I have an iMac and a macbook pro with 12,000 pictures on one and 12,500 on the other (mostly the same pictures.) How can I transfer one library to the other and not get duplicates of the pictures that are already on the other mac? Im trying to clean my macbook pro and only hold a few pictures. I have a time machine put don't want to fill it up with the 12000 duplicates. Thanks I am new to this forum and hope I have done this post correctly