[Gdal-dev] gdal newbie-merge/gdalwarp geotiff

[Izzy]

Hi,
I am trying to stitch together geotiff satellite images to obtain a world
satellite picture.

I experience problems with the colors in the output image when using
gdal_merge.py.  All the colors are fainted.  I suspect this has to do with
the fact that the input images have ColorInterp=palette but the palette has
values:0,0,0,255 for all 256 elements.  I have been looking around to
determine how I could use the the input images colors for the output with no
luck so far.  If I use -pct option with gdal_merge.py then my output image
is all black.
I tried using gdalwarp but I obtained a black output image even if I try to
just place one input image in the output.  Since I am not familiar with GDAL
or GIS area at all, I suspect I am not using gdalwarp correctly.  I tried:
gdalwarp input.tif output.tif
gdalwarp -s_srs 'ULx ULy LRx LRy' input.tif output.tif where the values
enclosed in quotes are the gdalinfo UL and LR coordinates for input.tif.
gdalwarp -t_srs '+proj=equirectangular +datum=WGS84' input.tif output.tif
input image projection=equirectangular

Is there any way to set the output color table that would give me an output
image with same colors I have on input images?

Are there documentation websites I could use to learn more about the usage
of the options to run gdal_merge.py or gdalwarp?
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