[Gdal-dev] extent of a file/map [2]

[Fulko van Westrenen]

On Tue, Jul 27, 2004 at 04:12:18PM -0400, Frank Warmerdam wrote:
> Fulko van Westrenen wrote:                                                                                           
> >Hello,                                                                                                              
> >                                                                                                                    
> >I have some python code to retrieve layer information from a                                                        
> >s57 file. This works nice, but I would like to know the area                                                        
> >covered by a file.                                                                                                  
> >                                                                                                                    
> >The documentation suggests the use of GetExtent, but that is                                                        
> >for a layer. What is the proper way to get the extent of a file?                                                    
>                                                                                                                      
> Fulko,                                                                                                               
>                                                                                                                      
> In general I think you would need to merge the extents of all the layers.                                            
> But I'm pretty sure that all S-57 layers return the extent of the whole                                              
> datasource so just using the extent of the first layer should be fine.                                               

Frank,

Thank you for your reply. I tried some code, but it does not behave as
expected:
  File "./mooring65.gtk.py", line 846, in load_objects
      feat = objects.GetNextFeature()
  File "/usr/lib/python2.3/site-packages/ogr.py", line 383, in GetNextFeature
    return Feature( obj = f_o )
TypeError: a float is required


A snippet of the offending code:

def load_objects(dataset,name,sumloc):
    try:
       objects=dataset.GetLayerByName( name )
    except:
       return sumloc
    if objects is not None:
       extent = objects.GetExtent(0)
       print extent
       feat = objects.GetNextFeature() #this is the line that generates the error
       while feat is not None:
          geom=feat.GetGeometryRef()

I inserted objects.ResetReading() after the print instruction, but
that didn't help much. I have the feeling I do not understand the
behaviour of osr. Any help is much appreciated.

Thanks,
Fulko
										    


-- 
Fulko van Westrenen
Fulko.vanWestrenen at DTO.TUDelft.NL