Is it possible to direct all printing to one specific color channel?

[Ramiro Chagas de Carvalho]

I was trying to find a way of printing white overlay with special white ink on Epson printers fed into one (or more) of the CMY channels.
In order to do that, I would need a mechanism to direct all non black pixels into one (or more) specific ink channels.
Is it possible to be done in Gutenprint by using printing options and/or XML config files?
In the doc folder there is a file named "5.0-release-plan.txt" including the following comment:

 * Applications with special requirements can now access the raw
   ink channels directly.  This facility was used to create a
   mechanism to more accurately tune printer inks.

Is that feature related to this topic? If so, how to accomplish that?

Thanks.

Ramiro.

[Gary Aitken]

You can probably do this by inserting a print filter in the output stream of gutenprint. I've never done this but I'm pretty sure you could do this by mapping the COLOR1 byte of the escp2 print command (ESC i) to your desired color. Since it is a byte-for-byte swap, it should have few ramifications (I think...)