[Gdal-dev] more problems

[Frank Warmerdam]

Vladimir,

OK, I have spent a few more hours hacking and have made several improvements:

  o I now write GTCitationGeoKey with the high level coordinate system
    description from the well known text.

  o It is now possible to update the projection information and metadata of
    a existing GeoTIFF file in place.  This may only work for uncompressed
    files ... I don't know it is currently supported to open compressed geotiff
    files in update mode.  This is a very new and experimental ability!

  o Metadata can be written to files created directly as well as those
    created with CreateCopy().

  o I added support for generic metadata.  Any metadata items other than
    the special TIFFTAG_* values will be written new a new tiff tag I have
    defined in a simple XML format, and they are also recovered when reading
    the file.  This metadata will only be meaningful to GDAL based applications
    but it should be useful for stuff like using GeoTIFF as the generic "import"
    format for raster data in applications like OpenEV.  Eventually I would like
    to use a similar mechanism to associate stuff like NODATA values with
    GeoTIFF bands.

Some of the above changes required bug fixes in libtiff, so if you use an
external libtiff please ensure it is rebuilt from CVS, or reconfigure your
GDAL to use the internal libtiff (which has been updated from the libtiff
CVS tree).

All testing and feedback on the new capabilities is appreciated.

For interest sake, I was able to use the following python script to test the
inplace update of information on tiff files:

import gdal
import sys
import osr

driver = gdal.GetDriverByName( 'GTiff' )

ds = gdal.Open( 'test.tif', gdal.GA_Update )

md = { 'TIFFTAG_DOCUMENTNAME' : 'Third test', 'OTHERINFO' : 'New value', 'NewTag' : 'This 
tags value' }
ds.SetMetadata( md )

srs = osr.SpatialReference()
srs.SetFromUserInput( '+proj=utm +zone=11 +ellps=WGS84' )
ds.SetProjection( srs.ExportToWkt() )
ds.SetGeoTransform( [ 100000, 10, 0, 50000, 0, -10 ] )

ds = None

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent