Since you are working locally all the urls that saved are in database for your images so you will need to change them urls by using a Search and replace plugin and export that database from your local phpmyadmin and save as file on your computer.
You will find some plugins you can use here http://wordpress.org/extend/plugins/search.php?q=search+and+replace&sort=
On your host account phpmyadmin you can import that sql file