Hi Tõnis,
I don't have much experience with DGN files, but it looks like there are a
bunch of limitations and caveats listed at http://www.gdal.org/drv_dgn.html.
The "seed file" in particular looks like something to investigate. Remember
that creation options can be passed into fiona.open as kwargs like
with fiona.open('example.dgn', 'w', driver='DGN', schema=schema,
crs=crs, seed='seed.dgn') as dst:
...
Hope this helps, and happy new year!
On Wed, Dec 31, 2014 at 12:01 AM, tõnis kärdi <tonis.ka...@gmail.com> wrote:
>
> Hi,
>
> I can't seem to get writing dgn files with fiona to work - it results in
> "ValueError: Null layer". The same script works fine for writing shapefiles
> and MI tabs.
> I managed to create a DGN file using QGIS and then read it using fiona. I
> don't know much about CAD files in general so I'm sure there's something
> I've missed totally, any pointers much appreciated.
>
> Here's how it goes:
>
> C:\>ogr2ogr --version
> GDAL 1.11.0, released 2014/04/16
> C:\>python
> Python 2.7.5 (default, May 15 2013, 22:44:16) [MSC v.1500 64 bit (AMD64)]
> on win32
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import fiona
> >>> print fiona.__version__
> 1.1.6
> >>>
>
> schema and properties read from the file created in QGIS
> except for schema['geometry'] which was set manually to LineString
> as fiona reports it as 'Unknown' when reading:
>
> >>> schema = {'geometry': 'LineString', 'properties':
> fiona.OrderedDict([(u'Type', 'int:2'), (u'Level', 'int:2'),
> (u'GraphicGroup', 'int:4'), (u'ColorIndex', 'int:3'), (u'Weight', 'int:2'),
> (u'Style', 'int:1'), (u'EntityNum', 'int'), (u'MSLink', 'int'), (u'Text',
> 'str')])}
> >>> properties = {u'Style': 0, u'ColorIndex': 0, u'Weight': 0, u'Level':
> 0, u'Text': None, u'MSLink': None, u'GraphicGroup': 0, u'EntityNum': None,
> u'Type': 14}
> >>> crs = {'lon_0': 24, 'no_defs': True, 'x_0': 500000, 'lat_2': 58,
> 'lat_1': 59.33333333333334, 'towgs84': '0,0,0,0,0,0,0', 'ellps': 'GRS80',
> 'y_0': 6375000, 'proj': 'lcc', 'units': 'm', 'lat_0': 57.51755393055556}
> >>>
>
> [...]
>
> >>> with fiona.open(
> ... 'd:/tmp/nna.dgn',
> ... 'w',
> ... 'DGN',
> ... schema=schema,
> ... crs=crs) as sink:
> ... sink.write(
> ... {'geometry': {
> ... 'type': 'LineString',
> ... 'coordinates': [
> ... [658513.3899922734, 6475203.499964565],
> ... [658467.8400262331, 6475236.229952499],
> ... [658486.4300012367, 6475258.259991983],
> ... [658528.96998106, 6475228.000044374],
> ... [658513.3899922734, 6475203.499964565]]
> ... },
> ... 'type': 'Feature',
> ... 'properties': properties})
> ...
>
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> with fiona.open('d:/tmp/nna.dgn', 'w', 'DGN', schema=schema, crs=crs)
> as sink:
> File "C:\Python27\lib\site-packages\fiona\__init__.py", line 156, in open
> encoding=encoding, layer=layer, vsi=vsi, archive=archive)
> File "C:\Python27\lib\site-packages\fiona\collection.py", line 132, in
> __init__
> self.session.start(self, **kwargs)
> File "ogrext.pyx", line 960, in fiona.ogrext.WritingSession.start
> (src/fiona/ogrext.c:15730)
> ValueError: Null layer
> >>>
>
> All the best,
> Tõnis
>
> p.s. tried writing DGN also using osgeo.ogr. For whatever reason the
> .CreateLayer(...) method always returns None...
>
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>
>
--
Sean Gillies
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