Michael,
I'm not totally sure if image composition really belongs to gdaldem. It
feels it is more generic than that, although making nice looking DEM
rendering is definitely a common use case. There's this long existing
Python script at
https://github.com/OSGeo/gdal/blob/master/swig/python/gdal-utils/osgeo_utils/samples/hsv_merge.py
that combines the hillshade and color-relief together.
In the ecosystem at large, ImageMagick has also a lot of compositing
operators: https://imagemagick.org/Usage/compose/
If we added a utility in GDAL, it would have to be decided if it allows
different georeferencing/extent of images to be composed together. That
would likely brings a bit of complexity, although using on-the-fly VRT
underneath could help making images with the same size, resolution, extent.
There's also the question of if we would need this to be able to operate
in a VRT-ish way (a new subset of VRT would then be needed), because
that would have a strong impact on the design, compared to having a
utility that materializes the output in a regular file format.
Even
Le 09/07/2024 à 03:12, Michael Sumner via gdal-dev a écrit :
Just an update, I have found out how to do this numerically. Will
consider a PR for gdaldem if I can make it work at some point.
Thanks, Mike
On Tue, Jul 9, 2024 at 7:31 AM Michael Sumner <mdsum...@gmail.com> wrote:
Is it possible to "layer" one image over another, the first at
full transparency and the second with partial transparency?
I'm thinking of combining a hillshade and a (partially)
transparent color-relief image, a visual enhancement technique.
(I know how to do this downstream in R and Python or similar, I'd
like to stay in C++'s warm embrace. )
I can go and find out what "over plot" means when it comes to
colour imagery, just wondering if there's anything in-built
already. This might be a nice additional mode to gdaldem (and is
what I thought "color-relief" meant, at first).
Cheers, Mike
--
Michael Sumner
Research Software Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsum...@gmail.com
--
Michael Sumner
Research Software Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsum...@gmail.com
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