Some question about function StartPage() in Rastertohp.c

[Zhang xin]

> "!Duplex || (Page & 1)" means "not double-sided or on an odd-numbered
> page".  "Page & 1" is the same as "Page % 2" but is faster.
>
> In this case, the HP driver needs to send certain commands for the
> front side of pages - when printing the back side, different commands
> need to be sent.

Thanks alot for your taught:)it's a great favor for me and my friends.Now my friends and me think it's feasible that to develop a filter to GDI for linux like Rastertohp.c,can we develop it use the model you have used?and is it necessary to relate it with GhostScript?