Christopher - You will very likely find that using different LZW compression options (particularly setting a small strip size) will slightly degrade compression performance while significantly improving read time. While I think your test data are valid, they only address one of many possible configurations and I wouldn't necessarily make broad generalizations about LZW from them.
However, I have generally found that LZW compression for photographic data is indeed not a good choice; I'm surprised you got it to perform as well as you did (in compression). - Ed Ed McNierney Chief Mapmaker Demand Media / TopoZone.com 73 Princeton Street, Suite 305 North Chelmsford, MA 01863 Phone: 978-251-4242, Fax: 978-251-1396 [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Christopher Schmidt Sent: Monday, February 25, 2008 8:57 PM To: discuss@lists.osgeo.org Subject: Re: [OSGeo-Discuss] 'lossless' JPEG2000 On Mon, Feb 25, 2008 at 04:31:34PM -0800, Michael P. Gerlek wrote: > Yup: Kakadu is not Open Source, as per the OSI definition of the term. > The only FOSS package I know of is OpenJpeg2000 (or something like > that); unfortunately, however, it is not suitable for geo-sized imagery > last time I looked. Yep. > (LZW tiffs are a reasonable option, as they are lossless and the LZW > patent issues have faded into the sunset.) The level of compression from LZW is poor by comparison, on aerial imagery: a test dataset compressed from 169MB to 83MB, and time to serve up a small portion was approximately the same as with JPG (6.1s jpg, 6.5s lzw, .5s uncompressed), but the JPG was compressed to 13MB, making it worth the cost; lzw doesn't pay for itself in the same way. (See numbers on http://wiki.openaerialmap.org/Serving_Data) Regards, -- Christopher Schmidt Web Developer _______________________________________________ Discuss mailing list Discuss@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/discuss _______________________________________________ Discuss mailing list Discuss@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/discuss