Re: Postscript and PM3D file size.

[Daniel J S. <dan...@ie...>]

Arnd Baecker wrote:

>On Wed, 3 Mar 2004, Petr Mikulik wrote:
>
>[...]
>
>  
>
>>2. Use "with pixels style" patch by Daniel at the "Patches" section on
>>sourceforge.
>>    
>>
>
>And in that case I think using RLE instead of the present scheme
>should reduce the file size by another relevant factor.
>(However, though this seems pretty straight forward,
>someone has to code this and at the moment I am completely
>busy with other stuff ;-)
>

Well, run length encoding is great for applications like fax data and 
the sort, i.e., a single bit image depth.  That's because there are 
typically long stretches of white space where the run length really 
achieves compression.  However, I'm not sure what RLE will get you in 
color or gray scale images.  My experience with angiography images and 
the sort is that maybe 50% lossless compression is the best on average. 
 There are forms of lossy compression, but this takes consideration.  If 
someone on the list has experience with compact representation of 
various image types, that would be helpful...

I feel that coding is half the problem.  The other half is simply making 
a decision what to do, i.e., agreeing on what the format or syntax 
should be.  It can in fact be a fun little project to implement some of 
these things.  I just went to the library and looked at the Adobe 
PostScript Standard book and picked the most flexible beginning format, 
which to me seemed to be ASCII85.  The reason is that it would be 
lossless compression (keeping everyone fairly happy from the start), 
various PostScript viewers would likely be able to read it, and there 
would be no question of whether we should use, say, and MPEG compression 
library routine.  That is, I didn't see any sense in going full tilt 
into writing, say, an MPEG routine if it wasn't certain it would get 
used or if the developers may decided using some existing library would 
be the smartest maintenance alternative.

Dan