shiva@well.sf.ca.us (Kenneth Porter) (04/30/91)
Remember that when changing the transfer function, you should
carry along the old definition. It may contain code to
compensate for a non-linear marking engine, or it may have been
previously modified by an enclosing application to achieve a
special effect.
================================================================
% We must call existing transfer function after ours
% for proper mapping of user grays to device grays.
/oldtransfer currenttransfer def
% Function just subtracts requested gray from 1, then
% calls device transfer function.
{ 1 exch sub oldtransfer } bind settransfer
% init page to logical "white"
gsave
1 setgray clippath fill
grestore
================================================================
Ken (shiva@well.sf.ca.us)