About PNG output. Uncompressed PNG.

[Ed McNierney]

Bob -

What is it you're trying to accomplish?  All PNG images are compressed,
in that they all use deflate compression on the data stream.  The data
stream is filtered first to optimize it for compression; while you can
control the choice of filter, I do not believe there is any control over
the compression.

The compression is completely lossless, so there is absolutely no
degradation of the image (as opposed to JPEG, for example).  Saying you
want "PNG with 0 compression" is sort of like saying "I would like
EXACTLY the same image in this file, just puff up the file to make it
bigger".

If you are simply trying to get the best quality PNG image, you've
already got it.  If you're looking for something else, let us know.
Thanks!

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com
(978) 251-4242  

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Bob Basques
Sent: Tuesday, January 10, 2006 4:40 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] About PNG output. Uncompressed PNG.

All,

I don't really know what I'm asking here, but here goes.

What Compression value does MapServer use for outputting PNG images?  
Can this be adjusted.  I'm interested in outputting PNG's with 0 (zero) 
compression.   Is there a setting somewhere for this?

bobb