[gdal-dev] gdal_merge.py alpha mask

[Chaitanya kumar CH]

Stefan,

I haven't tested the script but doesn't the current code copy the alpha
band? If it does, it might be more preferable to copy all the pixels and the
alpha band.

Please create a ticket at http://trac.osgeo.org/gdal/newticket and attach
your patch.

On Tue, Jun 29, 2010 at 8:19 PM, Stefan Klug <Klug.Stefan at gmx.de> wrote:

> Hi,
>
> gdal_merge.py doesn't handle tiff files with alpha masks so I've added this
> functionality.
>
> My patch changes the behaviour of gdal_merge as follows:
> - If a band is recognized as Alpha Band it is automatically treated as
> having a NODATA value of 0.
> I'm not sure if this is the way to go. But it makes some sense, as the
> resulting alpha channel is a correct alpha merge, independent of the nodata
> value used for the other bands.
> - If a band has mask flag GMF_ALPHA set, the mask band controls the parts
> that get written to the destination
>
> Would be great if someone could review and possibly checkin the patch.
>
> Regards
>    Stefan
>
>
>
>
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-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
17.2416N 80.1426E
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