[GRASS-dev] Problems with r.out.gdal byte export: colors modified in RGB multilayer GeoTIFF

[Markus Neteler]

Hi,

I am currently processing satellite data > 8bit and created a nice
"natural color" RGB composite (channels separated).
Using the #map operator of r.mapcalc I could successfully reduce each
channel to 8 bit, after i.colors.enhance the respective RGB composite
looks almost identical.
The scope is to process the data in GRASS GIS, then export them for a
performant OGC Web service.

So far so nice. Now, exporting it as a multilayer GeoTIFF (I made a
group of the 3 channels using i.group, then gave that as input to
r.out.gdal) leads to yellowish colors which are not the same any more.
Adding the -c flag did not help.

GRASS 7.1.svn (utm48n): > r.out.gdal -c input=rgb_group
output=rgb_8bit_flag_c.tif
Checking GDAL data type and nodata value...
 100%
Using GDAL data type <Byte>
 100%
Using GDAL data type <Byte>
 100%
Using GDAL data type <Byte>
Exporting raster data to GTiff format...
 100%
 100%
 100%
r.out.gdal complete. File <rgb_8bit_flag_c.tif> created.
[Raster MASK present]

Screenshot attached (top left: original; top right: reduced to 8 bit;
low: exported multilayer-RGB shown in QGIS).

I also tried the HFA driver, same issue.

What's the trick?

thanks
Markus
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