[gdal-dev] An issue about using GDALWARP todotheNTv2transformation

[heng.feng]

Thanks for your quick response, Uwe. Yes, all the tif files have got the same color table. I checked that and added the -pct option. But I think I forgot to remove the old merged one I generated without the -pct option. Now that I have removed the old merged one, a merged colored tif file is successfully generated after running the same command :)
________________________________
From: Schmitz, Uwe [via OSGeo.org] [ml-node+5954610-1691648657-308251 at n2.nabble.com]
Sent: 24 January 2011 09:24
To: Heng Feng
Subject: AW: [gdal-dev] An issue about using GDALWARP todotheNTv2transformation

Heng,

>
> Hi Uwe,
>
> I have been trying to use gdal_merge.py to merge
> a few 8 bit colored .tif tiles together. Having
> tried all sorts of options for this command, I
> always ended up with a merged 8-bit grayscale picture.
> I did a search on the internet and found a couple of
> posts related to this, however it seemed to me that
> the gdal_merge.py just does not have the ability
> to preserve the color. Did I get the wrong idea about
> this? Do you have any suggestion to solve this problem?
>
you have to specify "-pct" to grab the color table
of the first merged tile for the result file.
And, very important, all input tiles need to have
the *same* color table, because merging is done
on pixel values (that means channels).

> Not sure if I should post a separate message for
> this gdal_merge.py issue.  I just thought this would
> be the quickest way to get the help :)
>
Yes, IMO a seperate post would have been better and
addressing it to me wouldn't always help to get a fast
response ;-)

Regards
Uwe
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