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From: csb@gdwb.oz.au (Craig Bishop)
Newsgroups: comp.lang.postscript,comp.dcom.fax
Subject: Re: Compression of image matrices
Keywords: images, data compression,
Message-ID: <581@rome.gdwb.oz.au>
Date: 22 Mar 91 01:44:51 GMT
References: <11757@pasteur.Berkeley.EDU>
Sender: news@gdwb.oz.au
Followup-To: comp.lang.postscript
Lines: 27

gilge@ICSI.Berkeley.EDU (Michael Gilge) writes:

>We are often faced with the problem of transmitting large image matrices 
>to a postscript printer, e.g. sampled images or screen captures from X.
>This causes large transmission times and we are thinking about compressing
>the binary data before transmission. Together with the data, a postscript 
>decompression program is also send to the printer. The printer applies 
>the program to the data and kind of unfolds the original image matrix.

>Before we start writing anything, has anybody ever done something like that?
>Especially is there a postscript program to decode fax Group3 encoded
>bitmaps?

I had to do a similar thing recently. We used a SUN SPARCprinter, these
printers are just a raster engine with the postscript being decoded on
the SPARCstation and the raster image being written to the printer via
a fast video port. What is different is that we accessed the video port
directly. When it is not being used by lpr and printing postscript I
can open it up and pump bitmaps at it. The code is trivial. The speed
of printing is amazing.

A 400dpi 3456 x 5214 bitmap printed in less than 5 seconds. 

--
Craig Bishop			Geelong & District Water Board
Phone: +61 52 262506		61-67 Ryrie St Geelong
Fax:   +61 52 218236		Victoria 3220 Australia