Re: [gdal-dev] Reading a single pixel from multiple bands at the same time in python

[Ivan Lucena]

Ben,

Another alternative a little bit more flexible is to use ReadRaster() specifying your query window (1x1 or more), the 
automatic data type conversion and the list of bands you are querying from. I guess it wrapper RasterIO directly.

Note that the resulting buffer will be binary, not a numpy Array as in ReadAsArray(), but that is easy to convert using 
numpy.fromstring().

Regards,

Ivan

>  -------Original Message-------
>  From: Frank Warmerdam <warmerdam at pobox.com>
>  To: Benjamin Welton <benjamin.r.welton at wmich.edu>
>  Cc: gdal-dev at lists.osgeo.org
>  Subject: Re: [gdal-dev] Reading a single pixel from multiple bands at the same time in python
>  Sent: Feb 23 '10 22:25
>  
>  Benjamin Welton wrote:
>  > Hey,
>  >
>  >    Iv got a question on whether or not its possible to read a single
>  > pixel value from multiple bands using one GDAL call in python? The file
>  > working with is an ENVI BIP file that has a large number of bands
>  > (around 1000) and im looking for a way to reduce the python overhead by
>  > only making one single call into the GDAL library. GDALDataset::RasterIO
>  > seems like it might be the function i need to use but im 100% sure. If
>  > anyone has any suggestions or hints on whether or not this is possible
>  > that would be great.
>  
>  Ben,
>  
>  You can use the ReadAsArray() method on a gdal.Dataset to read multiple
>  bands in one call as an array object:
>  
>  ds = gdal.Open('/home/warmerda/public_html/world.tif')
>  d = ds.ReadAsArray(0,0,1,1)
>  print d
>  [[[11]]
>  
>    [[10]]
>  
>    [[50]]]
>  
>  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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