Hi,
There was indeed an issue with the -exact_color_entry mode. Will be
fixed per https://github.com/OSGeo/gdal/pull/10596
As your input band is integer, you can safely use -nearest_color_entry
or the default linear interpretation mode (potentially adding an entry
"12 0 0 0 0" in case you want to map values >= 12 to transparent)
Even
Le 14/08/2024 à 08:28, Daniel Mannarino via gdal-dev a écrit :
Hi all!
I'm having trouble getting gdaldem to work the way I believe it's
supposed to. In particular I have given it a single-band uint8 GeoTIFF
and tried to map the values to RGB bands via a colormap using exact
matching, but the resulting GeoTIFF is invariably all zeroes (as if
there were no matches). Using -nearest_color_entry or not specifying
-exact_color_entry yields the expected results, but I only want exact
matches. I have tried specifying values to match as both floats (0.0,
1.0, etc.) and ints (0, 1, etc.). Adding an alpha channel makes no
difference in this sense. Am I doing something wrong, or is there an
issue with gdaldem? Here are the commands I used, and a link to the
files in question:
gdaldem color-relief -co COMPRESS=DEFLATE -co TILED=YES -co
BLOCKXSIZE=256 -co BLOCKYSIZE=256 -co SPARSE_OK=TRUE -co
INTERLEAVE=BAND -exact_color_entry -alpha foo.tif colormap.txt
exact_foo_with_alpha.tif
gdaldem color-relief -co COMPRESS=DEFLATE -co TILED=YES -co
BLOCKXSIZE=256 -co BLOCKYSIZE=256 -co SPARSE_OK=TRUE -co
INTERLEAVE=BAND -nearest_color_entry -alpha foo.tif colormap.txt
nearest_foo_with_alpha.tif
gdaldem color-relief -co COMPRESS=DEFLATE -co TILED=YES -co
BLOCKXSIZE=256 -co BLOCKYSIZE=256 -co SPARSE_OK=TRUE -co
INTERLEAVE=BAND -alpha foo.tif colormap.txt gradient_foo_with_alpha.tif
https://drive.google.com/drive/folders/17q3zQAcOqPTo4f8-swWEgrpQ9sfufasR?usp=share_link
These commands were performed with GDAL 3.9.1 installed on MacOS/ARM
via Homebrew, though the problem also occurs in our AMD64 AWS
instances running Linux and GDAL 3.8.4 with the official Docker images
as a base.
Thanks for any help!
Daniel Mannarino
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