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Data bits across LGP2 stream

I have  some software that will produce a hardcopy of an 8-bit color screen on the Symbolics.
The LISP code involved simply sends each byte of data (==ONE screen pixel) as TWO hex digits
to the LaserWriter to be interpreted by PostScript. Therefore, a screenful of data which is ~1 MB 
on the Symbolics side has expanded to ~2 MB on the PostScript side. If I can send a full byte to
the LaserWriter I can cut the size of the PostScript data in half.

Question: how many data bits does an LGP2 stream transmit to the LaserWriter? 
That is, is the stream strictly 7-bit ASCII or 8-bit "extended" ASCII. The actual stream I am 
using is an instance of LGP::LGP2-BITMAP-STREAM, created with hci:make-hardcopy-stream.

On a related note, if the stream is a full 8-bits then what is the appropriate
function to send a single byte of data to the LaserWriter? Better yet, how can
I send a "string" of bytes (i.e., NOT a LISP string but a contiguous set of bytes)
to the LaserWriter. I am aware that LGP2 streams support the :string-out message,
but the method there just sends the :tyo message for each char in the string, which
in turn becomes a :show-char message and so on--not efficient nor appropriate.

	Len Charest	charest@ai-sun.jpl.nasa.gov