Full Size Attachement Page link / select image size


Normally when you click on an image on the WordPress gallery it will get you to the .jpg file directly ( medium or full size - depending how the template is made ).

This is the code

<a href=“<?php echo wp_get_attachment_url($post->ID); ?>” TARGET=“_blank”><?php echo wp_get_attachment_image( $post->ID, ‘medium’); ?> </a>
What i want is when a user click on the image to go to the full size attachment page - so to display the image inside the attachment page, not the jpg only …

My second question. If you look for example at autoblog.com gallery here: http://www.autoblog.com/photos/2014-chevrolet-silverado-first-drive/#photo-5868614/

users can select the size of the attachment they want to view ( small / medium / large ). How can be this implemented - so when a user clicks on medium for example, to have an template for medium size images, and one for large or full size images…

Thank you

Best regards