bradlee@cg-atla.UUCP (Rob Bradlee) (02/21/90)
I would like to adjust the transfer function by providing a 256 entry lookup
table for values 0-255. I'd also like to be able to switch back to the
default sometimes. Any advice from the experienced PS gurus would be most
appreciated.
Rob
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Wilmington, Mass. 01887 The Nordic Way: Ski till it hurts!jwz@lucid.com (Jamie Zawinski) (09/29/90)
In article <20829@well.sf.ca.us> shiva@well.sf.ca.us (Kenneth Porter) writes: > > As Jamie Zawinski points out, settransfer can also be used, > but you should modify his example to concatenate the new > transfer proc with the result of currenttransfer, so that > the result can be combined with previous transfer ops (the > most important being any builtin engine compensation). Hmm, how would you do that? I don't think { { currenttransfer exec 1 exch sub fade-factor mul 1 exch sub } settransfer } will work, because currenttransfer is going to return the currently-executing procedure, leading to infinite recursion. You could do something like /saved-transfer currenttransfer def { { saved-transfer 1 exch sub fade-factor mul 1 exch sub } settransfer } but that doesn't seem especially foolproof. -- Jamie
wiml@milton.u.washington.edu (William Lewis) (09/29/90)
In article <JWZ.90Sep28150050@kolyma.lucid.com> jwz@lucid.com (Jamie Zawinski) writes: >In article <20829@well.sf.ca.us> shiva@well.sf.ca.us (Kenneth Porter) writes: >Hmm, how would you do that? I don't think > > { { currenttransfer exec 1 exch sub fade-factor mul 1 exch sub } > settransfer } > >will work, because currenttransfer is going to return the currently-executing >procedure, leading to infinite recursion. You could do something like > > /saved-transfer currenttransfer def > { { saved-transfer 1 exch sub fade-factor mul 1 exch sub } > settransfer } > >but that doesn't seem especially foolproof. [ /currenttransfer load /exec cvx 1 /exch cvx /sub cvx fade-factor /mul cvx 1 /exch cvx /sub cvx ] cvx settransfer ? I think that'll work .. the reason "currenttransfer" is load/exec'd rather than just cvx'd is that otherwise it would be identical to the first example up there, with infinite recursion... Or, you could do { currenttransfer 1 exch sub fade-factor mul 1 exch sub } bind settransfer in which the bind does about the same thing as building the proc as an array did up there, except it binds *all* of it, not just the /currenttransfer. -- wiml@milton.acs.washington.edu Seattle, Washington (William Lewis) | 47 41' 15" N 122 42' 58" W "These 2 cents will cost the net thousands upon thousands of dollars to send everywhere. Are you sure you want to do this?"
jwz@lucid.com (Jamie Zawinski) (09/29/90)
In article <8301@milton.u.washington.edu> wiml@milton.u.washington.edu (William Lewis) writes: > > [ /currenttransfer load /exec cvx 1 /exch cvx /sub cvx fade-factor /mul cvx > 1 /exch cvx /sub cvx ] cvx settransfer ? [ ... ] > { currenttransfer 1 exch sub fade-factor mul 1 exch sub } bind settransfer > > in which the bind does about the same thing as building the proc as an > array did up there, except it binds *all* of it, not just the > /currenttransfer. Hmm... I think both of these are equivalent to my second example, > /saved-transfer currenttransfer def > { { saved-transfer 1 exch sub fade-factor mul 1 exch sub } > settransfer } which now that I think about it some more, I don't think has any problems. To be extra careful, you could do { /--dummy-- 1 exch sub fade-factor mul 1 exch sub } dup 0 currenttransfer put bind settransfer assuming I don't have "put"'s arguments in the wrong order. -- Jamie
shiva@well.sf.ca.us (Kenneth Porter) (10/05/90)
Actually, I think you want to put the old transfer function at
the *end* of the new transfer procedure to get the right
effect, since there's no guarantee that the two procedures are
commutative:
/newstuff { .... } def
% remember to disable packing so put can write into executable array
false setpacking % real code should save current packing state
{ newstuff 0 exec } dup 1 currenttransfer put settransfer
The resulting transfer proc is
{ newstuff <oldtransfer> exec }
Is currenttransfer a variable or an operator? If an operator, then the
following doesn't work:
{ currenttransfer } bind
If it's a variable, then you can just do this:
{ //currenttransfer exec }
Ken (shiva@well.sf.ca.us)