[gdal-dev] empty Gtiff from Python

Fri Oct 28 09:24:55 EDT 2011

I
reinstalled everything, and then still something went wrong. Here I
have to tell you a little more on my goal: I was trying to convert a
slice of opendap data into netcdf. For this I use Pydap (works well). 
 I found out that using an 2D array  populated in a loop was saved as
a GTiff without a problem, but the PyDap arrays were a problem. Turned
out that Pydap returns a big-endian 32bit integer ( '>i4' ).
Converting this to 'normal' int32 resulted in a perfect image:
 instead of :
 a = dataset['klasse'][1:9,1:9,5].array[:]
 I used:
 a = dataset['klasse'][1:9,1:9,5].array[:].view(dtype = 'int32')
 a[:] = dataset['klasse'][1:9,1:9,5].array[:]
 Is this something to request a ticket for in GDAL to support? Not a
real big deal, but it takes time to convert obviously.
  Tom
 On Fri 28/10/11 11:10 , "Chris Yesson" Chris.Yesson at ioz.ac.uk sent:
 Tom,
 I have just run your code exactly as you sent it (except for output
 path), with python 2.5.2 ang gdal 1.8.1.  The ouput file appears in
 order (gdalinfo output below).  The file opens and displays normally
in
 qgis trunk v 1.8.
 - Chris
 Gdalinfo output
 Driver: GTiff/GeoTIFF
 Files: output.tif
        output.tif.aux.xml
 Size is 10, 10
 Coordinate System is:
 LOCAL_CS["arbitrary",
     UNIT["metre",1,
         AUTHORITY["EPSG","9001"]]]
 Metadata:
   AREA_OR_POINT=Area
 Image Structure Metadata:
   INTERLEAVE=BAND
 Corner Coordinates:
 Upper Left  (    0.0,    0.0)
 Lower Left  (    0.0,   10.0)
 Upper Right (   10.0,    0.0)
 Lower Right (   10.0,   10.0)
 Center      (    5.0,    5.0)
 Band 1 Block=10x10 Type=Byte, ColorInterp=Gray
   Min=1.000 Max=1.000
   Minimum=1.000, Maximum=1.000, Mean=1.000, StdDev=0.000
   Metadata:
     STATISTICS_MINIMUM=1
     STATISTICS_MAXIMUM=1
     STATISTICS_MEAN=1
     STATISTICS_STDDEV=0
 Date: Fri, 28 Oct 2011 10:23:04 +0200
 From: Tom van der Putte 
 Subject: [gdal-dev] empty Gtiff from Python
 To: 
 Message-ID: 
 Content-Type: text/plain; charset="utf-8"
 Hi
 List,
  I'm trying to save a numpy array to a GTiff, which should be quite
 straightforward, considering all the examples available on the web.
 However, I get an file that is not readable by Qgis, is regarded by
 ArcMap to have only 0 and gdalinfo displays nothing on the values.
  I start with a ndarray, dtype = int32, shape = ( 10,10). It has
 integer values between 1 and 10. The code is as follows:
  import numpy as np
  from osgeo import gdal
  from osgeo import osr
  #np array
  a = np.ones((10,10))
  #coord-system
  sr_str = 'LOCAL_CS["arbitrary"]'
  sr = osr.SpatialReference( sr_str )
  #driver
  driver = gdal.GetDriverByName("GTiff")
  #dataset
  ds = driver.Create("D:tempoutput.tif", 10, 10, 1, gdal.GDT_Byte)
  ds.SetProjection( sr_str )
  ds.SetGeoTransform((0, 1, 0,0, 0,1))
  #write and close
  ds.GetRasterBand(1).WriteArray(a)
  ds = None
  The corresponding gdalinfo is:
  *********
  Raster dataset parameters:
    Projection:
 LOCAL_CS["arbitrary",UNIT["metre",1,AUTHORITY["EPSG","9001"]]]
    RasterCount: 1
    RasterSize (10,10)
  Using driver GeoTIFF
    Metadata:
      0:  AREA_OR_POINT=Area
    Image Structure Metadata:
      0:  INTERLEAVE=BAND
  Corner Coordinates:
    Upper Left (0, 0)
    Lower Left (0, 10)
    Upper Right (10, 0)
    Lower Right (10, 10)
    Center (5, 5)
  Coordinate System is:
  LOCAL_CS["arbitrary",
      UNIT["metre",1,
          AUTHORITY["EPSG","9001"]]]
  Band 1 :
     DataType: Byte
     ColorInterpretation: Gray
     Description:
     Size (10,10)
     BlockSize (10,10)
  *********
  I have tried both version 1.6.3 (I'm trying to make a Qgis plugin,
 and thus restricted to 1.6.3) as well as 1.8.1. I have also tried ds
=
 driver.Create("D:tempoutput.tif", 10, 10, 1, gdal.GDT_Int32), but
 that didn't make much difference.
  I tried to make a Surfer grid (GSBG), and this somewhat worked: it
 gave a nice picture, but the values were off the charts.
  Any clues as to what I'm missing here? Cheers,
  Tom van der Putte
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