531990 Image Delete and Resize

Hello, I have a large directory of images, many of which are no longer used. Those that are used are referenced in my sites database. Some of these images are large and have large file sizes. I would like to create a script or file that i can place in my image directory, and it will do the following: If the image is not in the database it will be deleted, if it is in the database it will be re-sized (the re-size should reduced file-size as well)