There are 2 useful algorithms made by software:
1. 2xSaI Advanced Scale and Interpolation engine
(C) Derek Liauw Kie Fa aka Kreed (http://elektron.its.tudelft.nl/~dalikifa/)
2. hq2x Magnification Filter
(C) Maxim Stepin (http://www.hiend3d.com/hq2x.html)
But there are a hardware implementation in newest VGAs to perform an antialiasing filter rendering.
And i don't know if there are other hardware filters like scanlines, etc.
So if someone here have some trail...

