Why do you need a macro for that?


Go to the master slides view, create a new layout and place an image placeholder which fills the entire slide. Go back to the normal view, click on the placeholder and select the image you need (or paste the image). This will automatically crop and scale the image to the right size.

Thank so much
It's ok for copy paste image or new file based on slide master that I made it
but what for a file which already contain images (copy paste will maintain orginal size, changing layout has no effect), so a macro will play a role here
Any suggestion?