Even,
merci beaucoup for your continuous help and support! Creating the fields
on the target layer and using the feature definition from the target
layer does indeed help :-). I even looked at the corresponding part in
ogr2ogr.py before writing to the list but I didn't realise that this
part was not implemented in my code. Many thanks again!
Frank
Am 25.02.2011 11:34, schrieb Even Rouault:
Selon Frank Broniewski<[email protected]>:
Hello,
I have a problem when converting datasources from one format to GML.
Whenever I export my source datasource to a GML - datasource the
attributes of the features are missing in the resulting gml file. Other
exports to formats like shapefile, kml or geojson have the attributes
included. When I use ogr2ogr the gml has attributes included. So my
question is: What's the difference between e.g. a kml and a gml
outputformat and why does one have attributes and the other doesn't?
I tried on windows using gdal 1.8 and on Hardy 8.04 with 1.7.x, and on
both there're no attributes with the gml.
Watching the below code, I'm in fact surprised that it actually works with
shapefile, kml or geojson...
I'm really surprised for shapefile since the call to Layer.CreateField() is
needed to create the appropriate columns in the .DBF. For GeoJSON, from a quick
code review, it might indeed work but you shouldn't rely on that. For KML, I
guess you only get the Name and Description but not ExtendedData.
I use the following code to transform from one format to another:
target_driver = driver_by_name(target_format_name)
target_datasource = create_datasource(target_driver, output_destination)
for layer in iterate_layers(source_datasource):
layer_name = layer.GetName()
geometry_type = get_geometry_type(layer)
target_layer = target_datasource.CreateLayer(layer_name, source_srs,
geometry_type)
# At that point, the layer has no fields.
feature_definition = layer.GetLayerDefn()
Here you need to use target_layer.CreateField() to create the fields of the
target_layer based on the source layer feature definition.
Something like (untested. might need some minor adjustments on method names)
# Populate the target layer with field definitions coming from the
source
layer definition
for i in range(feature_definition.GetFieldCount()):
target_layer.CreateField(feature_definition.GetFieldDefn(i))
# Now fetch the resulting target feature definition
target_feature_definition = target_layer.GetLayerDefn()
for feature in iterate_features(layer):
target_feature = ogr.Feature(feature_definition)
Here's the error : you create a target_feature with the source layer feature
definition. This is bound to fail (and possibly even crash). Replace with :
target_feature = ogr.Feature(target_feature_definition)
target_feature.SetFrom(feature)
target_feature.SetFID(feature.GetFID())
if transformation is not None:
geometry_reference = feature.GetGeometryRef()
geometry = geometry_reference.Clone()
geometry.Transform(transformation)
target_feature.SetGeometryDirectly(geometry)
target_layer.CreateFeature(target_feature)
Full code:
http://paste.pocoo.org/show/344283/
Python test file
http://paste.pocoo.org/show/344284/
We should probably add some testing (in the binding code possibly, or deeper in
OGR) to check that the feature passed to Layer.CreateFeature() has a feature
definition matching the Layer.GetLayerDefn(). I would think that most (if not
all) drivers relies on that assumpution, although I don't see it explicitely
documented in
http://gdal.org/ogr/ogr__api_8h.html#301d319111285a47fe6cda6e079214f8
Frank
--
Frank BRONIEWSKI
METRICO s.Ã r.l.
géomètres
technologies d'information géographique
rue des Romains 36
L-5433 NIEDERDONVEN
tél.: +352 26 74 94 - 28
fax.: +352 26 74 94 99
http://www.metrico.lu
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[email protected]
http://lists.osgeo.org/mailman/listinfo/gdal-dev
--
Frank BRONIEWSKI
METRICO s.à r.l.
géomètres
technologies d'information géographique
rue des Romains 36
L-5433 NIEDERDONVEN
tél.: +352 26 74 94 - 28
fax.: +352 26 74 94 99
http://www.metrico.lu
_______________________________________________
gdal-dev mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/gdal-dev
