[gdal-dev] GeoTIFF NoData

[Julierme Pinheiro]

Hi all,

Sorry if my question has been discussed here before. I followed 1
Answer/Option 2 of this post
<https://gis.stackexchange.com/questions/41472/setting-transparency-in-an-sld-file-for-a-4-channel-geotiff>to
convert  an image (GeoTIFF) external pixels RGB(255,255,255) to NoData.

So, I used the following command line using GDAL_TRANSLATE :

gdal_translate -a_nodata 255 -of GTiff
/home/julierme/Desktop/amazonia_sar/amapa/IMG/covmingrad/CSKS4_20161223204711_CSKS4_20170124204700_3_CovMinGrad_rgb.tif
/home/julierme/Desktop/amazonia_sar/amapa/IMG/covmingrad/CSKS4_20161223204711_CSKS4_20170124204700_3_CovMinGrad_rgb_nodata.tif

The reason I am doing this is because I had a boundary/border
RGB(255,225,225) in the image. So, I converted the entire image
(255,255,255) pixels to NoData. Now, here are my two issues:

1 - Even after setting the InputTransparentColor = FFFFFF in Geoserver as
mentioned in the post Option2, the image border is not transparent. The
border, got an ALPHA_BAND=0.0 surrounding the image. Instead of an
ALPHA_BAND, I need a NaN value for the border. So, I need to completely
remove the ALPHA_BAND and set the border to NaN.

2 - What could I do to convert to nodata only the RGB(255,255,255) image
external pixels, without affecting the internal ones?

Thank you for your time in advance.

Julierme
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