[gdal-dev] alpha mask to data value

[Chaitanya kumar CH]

William,

Try gdalwarp after removing the mask band. If that didn't work try
gdal_merge.py with -init set to 255.


On Wed, Apr 2, 2014 at 1:44 AM, William Kyngesburye
<woklist at kyngchaos.com>wrote:

> I've wrestled with various nodata issues in the past, now it's hitting me
> again...
>
> I'm using Photoshop to delete collars on scanned maps, creating an alpha
> mask.  GDAL has no problem with this.  What I want to do is merge maps
> together (after rectification), then set any remaining nodata areas to
> white, RGB 255,255,255.  Just dropping the extra alpha band doesn't work
> because nodata is set to 0,0,0, which is black.  The a_nodata option in
> gdal_translate just defines what existing value in the data is nodata.
>
> I tried using gdalwarp with the -dstnodata option which should set nodata
> values in the output to a specific value, but it carries along the alpha
> band and ignores dstnodata.
>
>   gdalwarp -dstnodata "255 255 255" in.tif out.tif
>   Processing input file in.tif.
>   Using band 4 of source image as alpha.
>   Using band 4 of destination image as alpha.
>
>
> -----
> William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
> http://www.kyngchaos.com/
>
> First Pogril: Why is life like sticking your head in a bucket filled with
> hyena offal?
> Second Pogril: I don't know.  Why IS life like sticking your head in a
> bucket filled with hyena offal?
> First Pogril: I don't know either.  Wretched, isn't it?
>
> -HitchHiker's Guide to the Galaxy
>
>
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-- 
Best regards,
Chaitanya kumar CH.

+91-9494447584
17.2416N 80.1426E
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