[gdal-dev] Problem with GetNoDataValue function

[Greg Coats]

I agree that unsigned byte does not support -128. Signed byte does support -127. Signed byte does not could support -128. I note that http://www.gdal.org/gdal_translate.html shows that gdal_translate supports 11 data types Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/CInt16/CInt32/CFloat32/CFloat64, and "Byte" is included, but I think this "Byte" refers to unsigned byte. I do not see any indication that gdal_translate supports signed byte. Greg

On Aug 6, 2010, at 12:23 PM, Even Rouault wrote:

> Filippo,
> 
> What is the format of that raster file ? Can you share a link to the dataset ? 
> or the output of gdalinfo at the very least
> 
> I'd note that -128 can only be considered a valid value for a 8bit raster if 
> the metadata item PIXELTYPE at band level is set to SIGNEDBYTE 
> (IMAGE_STRUCTURE metadata domain).
> 
> Best regards,
> 
> Even
> 
> Le vendredi 06 août 2010 18:08:56, Filippo Corò a écrit :
>> Hi List,
>> 
>> I have a problem with the function GetNoDataValue () of GDAL 1.6.2 ver. I
>> use some raster where the nodatavalue is equal to -128 and the pixel depth
>> is 8bit. Opening the raster with the following code (with pydev  end
>> python 2.6):
>> 
>> # Get the bands and block sizes
>> primoBand primoDs.GetRasterBand = (1)
>> noval primoBand.GetNoDataValue = ()
>> 
>> Get noval = 0.0 and not -128 as I expected.
>> Is there any option I can use to solve the problem?
>> 
>> Thanks in Advance
>> 
>> Greetings
>> Filippo Corò