subdomain to root folder

[handyaner]

hello

i want 3 subdomains
img1.domain.com
img2.domain.com
img3.domain.com

all these subdomains should redirect to the root
i.e.
before: http://domain.com/wp-content/uploads/Light.png
after: http://img1.domain.com/wp-content/uploads/Light.png

how can i do this

 

[ranz]

Domain pointers will do this.