Have all GUI textures in one PNG file. How to use now?

I have a complete set of images for use in a GUI, but all have been placed in a single image file.

I've been looking and wondering if I have to "cut" out all these and make them into single images to use them as background textures for my GUI buttons...

Or is there a way to simply reference "where" on the single image, the required button's texture is? I'm pretty sure it exists, and would like to know how to do this, if possible.

Thanks!