[OSM-dev] request for hosting of WMS layers

[Jukka Rahkonen]

Jean-Guilhem Cailton <jgc <at> arkemie.com> writes:

> How about free implementations of JPEG 2000
> (http://www.jpeg.org/jpeg2000/), such as JasPer
> (http://gdal.org/frmt_jpeg2000.html,
> http://www.ece.uvic.ca/~mdadams/jasper/) or OpenJPEG
> (http://www.openjpeg.org/) ?
> Best regards,
> Jean-Guilhem

JPEG2000 is, in theory, a fantastic file format especially for advanced users
who need lossless compression, support for multichannel imagery and bit depths
other than 8 bit per channel, and perhaps streaming image service through JPIP
protocol. However, JPEG2000 is not widely used and programs supporting JPEG2000
do it often in a very bad way. I think that the main reason for a rather poor
situation is the lack of free and high quality JPEG2000 libraries. My own
experience comes mainly from Kakadu, which is good but not free. However, it
seems to be easy to use also Kakadu libraries in such a way that the result is
much slower than what can be feeled by trying Kakadu demo applications.

For some years ago I compered the speed of Mapserver WMS service with JPEG2000
(with Kakadu driver), ECW and uncompressed tiffs.  At that time tiffs were
fastest, ecw reached 50% of the speed and JPEG200 only 25%. But that was long
time ago, and actually that test was comparing only different GDAL drivers and
results must not be generalised. However, even all our aerial images are
archived as lossless JPEG2000 files optimised for fast serving, on the server
disks we have tiffs.

-Jukka-