[Gdal-dev] Accessing Raster Attributes

Frank Warmerdam warmerdam at pobox.com
Wed Mar 12 11:56:15 EST 2003

Oliver Wesp wrote:
> Dear List,
> what we like to do, is accessing the class_names attribute form ERDAS 
> img-Files (hfa).  We thought  **GDALGetRasterCategoryNames( 
> GDALRasterBandH hBand )  should to the trick, but it points to 
> GetCategoryNames()  and this function returns null. Maybe we're on the 
> wrong track anyway but this looks like it's not implemented.
> We would not hesitate to develop this by ourselfs but maybe this has 
> done before or someone can point us to the right direction.


This hasn't been done yet, but would be a worthwhile improvement.  If you
want to implement this, you would need to override the default implementation
of the GetCategoryNames() method on the HFARasterBand class in gdal/frmts/hfa.
You can use the low level HFA API to get the category names from the Erdas
file though I don't know the structure off hand.   You can use the "hfatest"
application in gdal/frmts/hfa to dump the file structure to try and pick out
the location of the category names.

If this gets to messy for you, email me a small .img file with category names
and I will look into implementing it.

Best regards,

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

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