[FWTools] (no subject)

[Travis Kirstine GIS Tech]

Frank,
The reason for my last question is that I have had few strange results from
the gdal_merge command.  I have been merging together overlapping RGB images
with different resolutions (30cm and 20cm).  The 20cm image has a no data
value of 0 0 0.  My basic command is:
gdal_merge.bat -o output_30cm.tif -of GTiff -n 0 30cm_input.tif
20cm_input.tif
The problem I'm finding is that areas that are near black (0, 7, 15) are
being converted to values with higher red values (80, 9, 19).

Travis

-----Original Message-----
From: fwarmerdam at gmail.com [mailto:fwarmerdam at gmail.com]On Behalf Of
Frank Warmerdam
Sent: Thursday, January 05, 2006 3:14 PM
To: Travis Kirstine GIS Tech
Cc: Fwtools
Subject: Re: [FWTools] gdal_merge no data values


On 1/5/06, Travis Kirstine GIS Tech <tkirstine at jdbarnes.com> wrote:
> Hi all,
> Is there a way to assign a no data value for all bands in a RGB image
using
> gdal_merge
> i.e. gdal_merge.bat -o merged.tif -of GTiff -n 0 0 0 rgb_image_1.tif
> rgb_image_2.tif

Travis,

I *believe* that if you specify a nodata value using the -n flag,
it will be used for all bands.

eg.
gdal_merge.bat -o merged.tif -of GTiff -n 0 rgb_image_1.tif rgb_image_2.tif


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