Pcking up two numbers from an expression via regex

I have expressions in a file that contain the string
"... width="100" height="200" ... ".
How can I pick up, via regex, the two numbers, "100", "200", which
actually vary from line to line, and change them to something else?
In short, I need to pick up the numbers following
"width" and "height", respectively, and change them to new ones.
Thanks!

maria