Worked for me using the following:
#Change black to white
gdalbuildvrt -srcnodata 0 -vrtnodata 255 to-be-decollared.vrt
to-be-decollared.tif
#Run nearblack -white
nearblack -white -o decollared.tif to-be-decollared.vrt
Luke
-Original Message-
From: gdal-dev-boun...@lists.osgeo.org
[mailto:gdal-dev-boun...@lists.osgeo.org] On Behalf Of Matt Wilkie
Sent: Thursday, 28 April 2011 1:57 AM
To: gdal-dev
Subject: [gdal-dev] nearblack troubles
Hi All,
The geotiff here
(http://www.maphew.com/Itches/Decollaring_with_nearblack) has two
collars to be removed. The outermost consists of pure black (0,0,0)
while the innermost is off-white (ranges from 240 thru 255). I used
gdalsetnull[1] to change 0,0,0 to nodata, then ran `nearblack -white` on
the result. I detect no difference in the output image even with a very
large fuzz factor (-near 50) .
What am I doing wrong?
{{{
d:\>cmd /version
Microsoft Windows [Version 6.1.7600]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
d:\>gdalinfo --version
GDAL 1.8.0, released 2011/01/12
d:\>gdalinfo to-be-decollared.tif
...snip
Band 1 Block=375x7 Type=Byte, ColorInterp=Red
Band 2 Block=375x7 Type=Byte, ColorInterp=Green
Band 3 Block=375x7 Type=Byte, ColorInterp=Blue
d:\>copy to-be-decollared.tif 0-is-nodata.tif
d:\>gdalsetnull 0-is-nodata.tif
Initial nodata for band 1 None
Output nodata for band 1 0.0
Initial nodata for band 2 0.0
Output nodata for band 2 0.0
Initial nodata for band 3 0.0
Output nodata for band 3 0.0
d:\>gdalinfo 0-is-nodata.tif
...snip
Band 1 Block=375x7 Type=Byte, ColorInterp=Red
NoData Value=0
Band 2 Block=375x7 Type=Byte, ColorInterp=Green
NoData Value=0
Band 3 Block=375x7 Type=Byte, ColorInterp=Blue
NoData Value=0
d:\>nearblack -white -near 50 -o no-collar-white.tif 0-is-nodata.tif
d:\>gdalinfo no-collar-white.tif
...snip...
Band 1 Block=64x64 Type=Byte, ColorInterp=Undefined
Description = Layer_1
Metadata:
LAYER_TYPE=athematic
Band 2 Block=64x64 Type=Byte, ColorInterp=Undefined
Description = Layer_2
Metadata:
LAYER_TYPE=athematic
Band 3 Block=64x64 Type=Byte, ColorInterp=Undefined
Description = Layer_3
Metadata:
LAYER_TYPE=athematic
}}}
[1]
http://code.google.com/p/maphew/source/browse/trunk/gis/o4w_extras/bin/g
dalsetnull.py
thanks in advance for your time and thoughts,
--
matt wilkie
Geomatics Analyst
Information Management and Technology
Yukon Department of Environment
10 Burns Road * Whitehorse, Yukon * Y1A 4Y9
867-667-8133 Tel * 867-393-7003 Fax
http://environmentyukon.gov.yk.ca/geomatics/
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