🚀 go-pugleaf

re: laser printers
   
   I admit that I may have been hasty in stating that a bitmap is
necessary for a laser printer (as I have been reminded more than once).
However, because of the mechanical nature of the laser printer (a 
photocopier with a laser light input) the image must be available at the
rate required by the printer.  Thus the full description of the page to be 
printed must be 'local' to the processor feeding the laser.  Either the 
processor must be able to generate the dots for the laser on the fly (a
question of processor speed and local memory) or it must form the bitmap and 
then stream it to the laser.  For some applications, the bitmap is a very 
useful solution to the problem.  In doing Tektronix 4010/4014 emulation, any
portion of the page can be written at any time.  So, constructing a bitmap from
the incoming move/draw commands is easier than than reprocessing the commands
for each local pass or band of laser printing.  However, for some things like 
ASCII text it makes sense to do it on the fly, as you don't write to the same 
place again.  It comes down to matter of what processor capabilites (read 
expense) are put into the laser printer.  The argument for doing every thing 
on the fly is that as soon as the page is formed, printing can start without
waiting for the bitmap to be finished.  With memory getting cheaper, one can
have enough memory for two bitmaps, and be printing the image from one, while
forming the image for the next page in the other.  
   The "full" capability 'on the fly' laser printers are not cheap.  The 8 page
per minute Talaris and Imagen printers are in the 8k$ range.  Most of that cost 
is for the intelligent printer electronics.  The higher cost for faster or
higher volume printers goes for a large part to the increased cost of the
photocopier engine.  As an example at the low cost end, the differences between
the capabilities of different model of HP Laserjets to do graphics (150 dpi vs.
300 dpi full page) is directly related to the size of the bitmap that the 
printer can hold.

          Jess Neri

Neri@nrl.arpa            DISCLAIMER:  I'm on my own on this too!

"Just remember, no matter where you go, there you are."
                                   - Buckaroo Bonzai
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