What your wanting "auto resize" requires that the object be written in vector format, not bitmap.

In vector (such as AutoCAD or similar) an object that is so small it can fit 1,000 times on the head of a needle can be blown up to the size of football field and still have the same appearance of detail because it is all done proportionally with mathmatics. A bitmap is not handled in the same manner.

Here are a couple links to further describe this.

http://www.mustek.com/class/bit_vec.html

http://tuts.cit.nih.gov/dtpcourse_vargas/A04-bitmapvsvector.html