[gdal-dev] Re: Creating a blank raster from scratch

[Jorge]

And finally, hello

Sorry for being annoying. I've found this ticket closed 2 years ago
http://trac.osgeo.org/gdal/ticket/1166.

I'll apply the patch, but I think that this should be added with the
FAQ. Saves time :-)

Best regards
Jorge

Jorge escribió:
> Hello again,
>
> I' ve found the problem, I think. Is the version of numpy used by
> gdalnumeric. The code from FAQ works with numpy version 1.0.1, but fails
> with numpy version 1.2.1. The fail is because the narray attribute
> "typecode()" doesn't exist. From the numpy book, available at
> http://numpy.scipy.org/numpybook.pdf, you can get (page 55):
>
> "If you are converting code from Numeric, then you
> will need to make the following (search and replace)
> conversions: .typecode() --> .dtype.char;
> .iscontiguous() --> .flags.contiguous;
> .byteswapped() --> .byteswap(); .toscalar()
> --> .item(); and .itemsize() --> .itemsize. The
> numpy.oldnumeric.alter code1 module can automate this for you."
>
> Ok. I've opened gdalnumeric.py, and the last change was from 2006/03/21.
> The older version from numpy available at sourceforge download's page is
> from 2007-11-08. Then, gdal is using a really old version of numpy.
> Maybe I can use the numpy 1.0.1 from my mac, but I think that it would
> be easier to replace the snippet's code lines that uses numpy from the
> correct ones. What's the best way to do this
>
>         # Create blank raster with fully opaque alpha band
>         zeros = numpy.zeros( (tiff_height, tiff_width), numpy.uint8 )
>         dst_ds.GetRasterBand(1).WriteArray( zeros )
>         dst_ds.GetRasterBand(2).WriteArray( zeros )
>         dst_ds.GetRasterBand(3).WriteArray( zeros )
>         opaque = numpy.zeros((tiff_height,tiff_width), numpy.uint8 )*255
>         dst_ds.GetRasterBand(4).WriteArray( opaque )
>
> by using gdal? Because, if I'm right, this snippet from the FAQ is
> deprecated.
>
> Regards
> Jorge
>
> Jorge escribió:
>   
>> Hello everybody
>>
>> I'm creating a blank raster from scratch, to rasterize it later. Ok,
>> I've read the FAQ:
>>
>> http://trac.osgeo.org/gdal/wiki/FAQRaster#HowcanIcreateablankrasterbasedonavectorfilesextentsforusewithgdal_rasterize
>>
>> I've executed this code with no problems in a Mac, with Leopard. I've
>> used the frameworks at http://www.kyngchaos.com/software:frameworks. The
>> version of GDAL is 1.6.0, and the numpy version is 1.0.1 Now, I try to
>> execute the code in another machine, a PC with Suse Linux Enterpise 11.0
>> for 64bits processors. I've installed gdal and numpy from repositories.
>> The version of GDAL is 1.6.0, and numpy version is 1.2.1  So, the gdal
>> versions are the same. But if I open, for example, the file ogr.py in
>> both systems, are different files. Maybe the Framework I'm using is a
>> port of GDAL 1.6.0 to Mac with any changes?
>>
>> And another issue: the code fails in the PC with Suse. The first error is:
>>
>> src_lyr = src_ds.GetLayerByIndex( index = 0 )
>> AttributeError: DataSource instance has no attribute 'GetLayerByIndex'
>>
>> I could solve the problem by changing the call to "GetLayerByIndex(
>> index = 0 )" for "GetLayer( 0 )". Why is this happening, if the version
>> of GDAL is 1.6.0 on both systems? Again, I think that maybe the
>> Framework I'm using is a port of GDAL 1.6.0 to Mac with any changes.
>>
>> Then, made this change, I get another error, that I couldn't solve yet
>> (create_raster.py is the name of my file):
>>
>>  File "./create_raster.py", line 112, in ?
>>     dst_ds.GetRasterBand(1).WriteArray( zeros )
>>   File "/usr/lib64/python2.4/site-packages/gdal.py", line 876, in WriteArray
>>     return gdalnumeric.BandWriteArray( self, array, xoff, yoff )
>>   File "/usr/lib64/python2.4/site-packages/gdalnumeric.py", line 193, in
>> BandWriteArray
>>     datatype = NumericTypeCodeToGDALTypeCode( array.typecode() )
>> AttributeError: 'numpy.ndarray' object has no attribute 'typecode'
>>
>> So, basically, the method "BandWriteArray" of gdalnumeric.py is
>> expecting an object array, with a method named "typecode()", but the
>> array created with numpy.zeros, don't have this attribute. Am I right?
>> Then, the fact is that in version 1.0.1 of numpy, the array created with
>> numpy.zeros has a method named "typecode()", but in version 1.2.1, this
>> attribute doesn't exist. Do I have to "downgrade" the numpy version from
>> 1.2.1 to 1.0.1 to make the code works in suse? Is there another
>> solution? Sorry for this kind of questions, but I'm very newbie with Python
>>
>> Thanks in advance!
>>
>> Regards
>> Jorge
>>
>>
>>
>>
>>
>>   
>>     
>
>   

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