i am using the latest version of ploggeer i had implemented lightbox in my site so at album level the link goes straight to large thumbnail when clicked on thumbnail .i need to go to the larger version of image so i need a link at bottom of each thunbnail to go to the the url of image ie a link calling the function plogger_get_source_picture_url() saying Largeimage
What are you asking? It seems that you already know what you need to do to get this to work. You just have to implement you code in 'album.php' in the theme of your choice. I'm not sure what other information you need.
It would be something like this: <a href="<?php echo plogger_get_source_picture_url(); ?>" rel="lightbox">Large image</a>