Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!umich!yale!mintaka!bloom-beacon!eru!luth!sunic!kth.se!news
From: d87-jse@garbo.bion.kth.se (Joakim Sernbrant)
Newsgroups: comp.lang.postscript
Subject: Re: Bitmap decompression wanted
Message-ID: <1990Jul5.205445.8084@kth.se>
Date: 5 Jul 90 20:54:45 GMT
References: <8561@cognos.UUCP>
Reply-To: d87-jse@kth.se (Joakim Sernbrant)
Organization: Royal Institute of Technology, Stockholm, Sweden
Lines: 26

In article <8561@cognos.UUCP> donc@cognos.UUCP () writes:
>I have found that sending large bitmaps to my PostScript printer is one of my
>biggest bottlenecks. I read in the 'green' book that compressing a bitmap
>first and decompressing it in the data acquisition procedure could save some
>time. The green book says ...
>   "This may drastically reduce transmission time, but it is quite
>   difficult to make the procedure fast enough to realize a net gain in
>   overall evaluation time."
>
>Has anybody written such a procedure? I would like to try it out on my sample
>data to see if it would gain me anything.
>   Any code or ideas would be appreciated.
>
>                      Don

I have spend many hours on this matter. I have tried runlength
encoding and packing six bits into each byte in the image.
The result have been dissapointing. Everything I've tried has
actually been mush slower than normal. This has been tried mostly
with 256 colors GIF images; special images with large white/black
areas can be handled with runlength encoding with good results.

Jocke
--  Joakim Sernbrant, Royal Institute of Technology, Stockholm, Sweden
--  Internet:  d87-jse@nada.kth.se
--