[gdal-dev] Re: 254 into 255

[Chaitanya kumar CH]

What was the nodata value in the original?

On Fri, Oct 28, 2011 at 11:28 PM, Hermann Peifer <peifer at gmx.eu> wrote:

> On 27/10/2011 10:58, Chaitanya kumar CH wrote:
>
>>
>> A vrt file can implement your requirements. It can create a 'lookup
>> table' to translate your pixel values...
>>
>
> Chaitanya,
>
> I just tried to translate an Int32 GeoTIFF with pixel values 111..523 into
> a byte-type GeoTIFF with values 1..44, using the LUT as indicated below.
>
> I noted that in the resulting GeoTIFF, the previous NODATA areas have now a
> pixel value of 1. Is this expected behaviour or rather some sort of
> "over-extrapolation" of my lookup table (as I would assume)  ?
>
> Thanks in advance, Hermann
>
>
>
> <VRTDataset rasterXSize="8786" rasterYSize="6443">
> ...
>    <VRTRasterBand dataType="Int32" band="1">
>    <NoDataValue>0.**00000000000000E+00</**NoDataValue>
>    <ColorInterp>Gray</**ColorInterp>
>    <ComplexSource>
>      <SourceFilename relativeToVRT="1">ch00_form.**tif</SourceFilename>
>      <SourceBand>1</SourceBand>
>      <SourceProperties RasterXSize="8786" RasterYSize="6443"
> DataType="Int32" BlockXSize="256" BlockYSize="256" />
>      <SrcRect xOff="0" yOff="0" xSize="8786" ySize="6443" />
>      <DstRect xOff="0" yOff="0" xSize="8786" ySize="6443" />
>      <LUT>111:1,112:2,121:3,122:4,**123:5,124:6,131:7,132:8,...</**LUT>
>    </ComplexSource>
>  </VRTRasterBand>
> </VRTDataset>
>



-- 
Best regards,
Chaitanya kumar CH.

+91-9494447584
17.2416N 80.1426E
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