[gdal-dev] gdalwarp question - probably pretty simple

[Etienne Tourigny]

I think only one alpha band is supported?

On Fri, Nov 23, 2012 at 2:08 PM, David Strip <gdal at stripfamily.net> wrote:
> On 11/22/2012 10:40 PM, David Strip wrote:
>>
>> I've got a geotiff which gdalinfo reports as 2 bands, with band 2
>> interpreted as alpha. The projection is Maryland State Plane. The color
>> table is paletted, with NO_DATA = 0
>> I can view this file in OpenEV with no problem
>> I call
>>     gdalwarp -t "WGS84" input.tif output.tif
>> When I open the resulting file in OpenEV, I see nothing, the screen
>> appears to remain black. When I move the cursor around, it reports the value
>> as NO DATA.
>>
>> I thought this might have something to do with the alpha band, so I added
>> - dstalpha. This produces
>>     ERROR 6: SetColorTable() not supported for multi-sample images
>> It still completes and produces a file, but gdalinfo doesn't report band2
>> as alpha, and I still get a blank view in OpenEV.
>>
>> I suspect I'm missing something quite basic, but I'm not seeing any
>> obvious command option.
>
>
> I can make this work if I first strip out the alpha band
>     gdal_translate -b 1 input.tif output.tif
>
> But I'm still interesting in hearing how I could make gdalwarp work
> directly.
>
>
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