Hi all, I have been using the GDAL command line tools to pre-process various kinds of remote sensing imagery datasets in GeoTIFF format. This includes resampling 16 bit images (eg. from Landsat 8) to 8-bit and to combine bands into RBG composites.
In GDAL 11.4 (and previous 11.x that I tried), this doesn't work any more: gdal_translate -ot Byte -scale [sceneID]_Bn.tif [sceneID]_8bit_Bn.tif I usually apply this to the already clipped RGB composites, but digging deeper, even for single-band images what seems to be happening is that the -scale option doesn't correctly calculates the source range: - If I use the command above, or with -scale_1, the whole output file has a value 0 for each pixel - If I use the "-b 1 -scale", the whole output file has a value 255 at each pixel - If I use "-scale src_min src_max" with a manually inserted src_min and src_max, I get a reasonable result (though not necessarily identical to the GDAL result with automatically calculated min and max. What is driving me absolutely bonkers, though, is that *occasionally* the command "-b 1 -scale" DOES produce a correct 8-bit file. It's not reproducible, though: if I delete all 8bit files and re-run the script over a whole set of 16 bit files, a whole different file may be resampled correctly. With GDAL 2.0.2, my old script (written when GDAL was at 1.8.x on my machine) seems to be working at the moment, but my main system is currently at 11.4, and I have a reason not to upgrade right away. Is there a way to make it work with 11.4? I could run gdalinfo first and extract min and max from the stats, and then feed this into gdal_translate, but I'd like to avoid this path if possible. A test file (a file subsetted with "gdal_translate -projwin... " from a whole Landsat 8 band) is here: http://www2.gi.alaska.edu/~cwaigl/images/LC80660142015170LGN00_B5_clip.tif (3.8 MB). Thanks for your help, Chris -- Christine (Chris) Waigl - cwa...@alaska.edu - +1-907-474-5483 - Skype: cwaigl_work Geophysical Institute, UAF, 903 Koyukuk Drive, Fairbanks, AK 99775-7320, USA
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