PHP Mapscript - Jpeg2000

[Norman Barker]

-----Original Message-----
From: Shoaib Burq [mailto:hydromap at gmail.com]
Sent: Friday, December 16, 2005 1:21 PM
To: Norman Barker
Cc: MAPSERVER-USERS at lists.umn.edu
Subject: Re: [UMN_MAPSERVER-USERS] PHP Mapscript - Jpeg2000


> Thank you for your help, I will try to get this working.  Jpeg2000 offers lots of benefits, and seems to work really well with MapServer (I was using FWTools on Windows before I needed php support), the resolution pyramids in Jpeg2000 avoid the need to use gdaladdo (correct me if I am wrong!), and offer excellent compression as well!
>
Norman,

I was under the impression that for performance its better to steer
clear of compressed formats in Mapserver due to the decompression
overhead? How much data are u serving?

shoaib

Hi Shoaib,

Jpeg2000 is becoming the standard image data format, as illustrated by a recent posting on the OpenGIS web site about a NATO tender (http://www.opengeospatial.org/press/?page=newsletter&year=0&newsletter=90).  The reasons are compression, open standards to name a few, but I can expand if interested.

As I understand it GDAL uses either Kakadu or the ERMapper SDK to utilise Jpeg2000, these are highly optimised libraries.  Jpeg2000 (and I believe all wavelet based file formats) allow you to only 'pull' out the section (and resolution) of the image that you are interested in, therefore actually reducing the time taken to get your data, which is different to standard compression algorithms.  So you can have a multi-gigabyte image on disk and pan and zoom it quite effortlessly.  The equivalent is a uncompressed geotiff pyramid which will (if non-lossy) be several magnitudes larger (ok you can pick Jp2 profiles that make the image huge).  I think Jukka, and myself, are both serving Jpeg2000 files that are many gigabytes in size.

I am getting excited about the GML in Jpeg2000 that Frank and others have been working on, and I hope that this can be incorporated into MapServer and some cross of WFS / WMS, or perhaps as it should be, a Web Coverage Service format.

JPIP streaming is a nice benefit and allows interactive streaming of large dataset in low bandwidth (or large load) server environments.  RSI (my employer) have a product IAS, as do ERMapper (Image Web Server), and Kakadu also have a demo with their binaries (kdu_show, kdu_server).  This is different to the Ajax Map type of application, allowing progressive rendering of image tiles.

I would like to discuss the GML in Jp2 format a bit more, I know we had a brief discussion several months ago in relation to n-d data, but I think things have moved on significantly now.

Many thanks,

Norman