Shrink an image

Is it possible to shrink an image with jQuery when the page loads? I understand how to shrink a div but not an image.

You can make an image appear smaller on the screen, but it’s still the full-size image that is downloaded from your server.

Yes that would be fine - what I am hoping for is that the full size image displays and then after a time delay the image shrinks to half its size. I managed to get it working, but it is complicated by the fact that the image is in a container div which I also want to shrink at the same time, and keep both centered on the page.