Changing the supplied image code? (after uploading an image)

After you upload an image in WP it supplies you with a tag like this:

Here’s the code to display it:
img src=';/images/font_smoothing.jpg'

I would like to make the code say:
img src='http://www.planetkris.com/images/font_smoothing.jpg'

With the full domain name supplied.
Where / how could I change that?

For the time being I’ll manumatically add it. 🙂
– Kris