Selon Ivan Lucena <[email protected]>: > Frank, > > I am having a similar problem with a files like that. They are taking more > than 3 seconds just to open on gdalinfo or any GDALOpen() call. That wouldn't > be a problem except in a case where we are running a large bath process with > several gdal_translate runs frequently.
IMHO, the opening time has nothing to do with the presence of GCPs. I would suspect that your NITF file is JPEG2000 compressed and that there's a slowdown due to the underlying JPEG2000 driver that is used. You could try to switch to another JPEG2000 driver to see if things improve. > > But as far I can tell the GCP are right on the corner pixels, so it would be > very fast to interpret it as a GeoTransform matrix. Would that be safe to > change the driver's code to do that? The code is already supposed to try to transform the GCPs in a GeoTransform. If the interpolation is exact, the GeoTransform will be returned, otherwise the GCPs. You might want to track what happens in the GDALGCPsToGeoTransform() function called at line 1040 of nitfdataset.cpp > > Regards, > > Ivan > > > > -------Original Message------- > > From: Frank Warmerdam <[email protected]> > > To: Logan Greenlee <[email protected]> > > Cc: [email protected] <[email protected]> > > Subject: Re: [gdal-dev] NTF/JPEG2000 Question > > Sent: Jul 17 '11 10:32 > > > > On Sun, Jul 17, 2011 at 8:16 AM, Logan Greenlee > > <[email protected]> wrote: > > > Sorry - here are the GCP's: > > ... > > > Is there any particular reason mapserver can't use the GCP's for > display? Is it that they are not necessarily corner points of the image? > > > > Logan, > > > > It is just not a feature of MapServer to support warping > > (rubber sheeting) of images on the fly based on GCPs. It > > would be fairly computationally expensive to do this so I > > deemed it not very useful in MapServer. It also isn't something > > I've seen requested often. > > > > However, MapServer does support reprojecting images on > > the fly which is similarly computationally expensive, so it > > might make sense to add a mechanism to MapServer to use > > gdal transformers (such as polynomial warping using GCPs) > > as an option. It would require some development. > > > > Best regards, > > -- > > > ---------------------------------------+-------------------------------------- > > I set the clouds in motion - turn up | Frank Warmerdam, > [email protected] > > light and sound - activate the windows | http://pobox.com/~warmerdam > > and watch the world go round - Rush | Geospatial Software Developer > > _______________________________________________ > > gdal-dev mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev > _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
