Using: QGIS 3.24.0 Tisler, ImageMagick 7.2.0-29, both Windows 64 bit on Windows 10. The computer has 96GB of RAM and all the software is 64 bit builds, so I don't think it's a shortage of memory.
I have some ALOS 30m heightmap data in GEOTiff format that I am trying to get a softer hillshade of it to use as the background for a map.
When I load the original file (copied from the ALOS original ALPSMLC30_N032E010_DSM.tif), it will hillshade fine and display the hillshading if you select Raster->Analysis->Hillshade from the menu.
The range of values in the original comes out at 23-642 (see below)
In order to do this, I am resampling the file using Imagemagick to interpolate from 30m to a 3m pseudo-scale.
magick convert Tataouine30m.tif -filter Spline -resize 1000% Tataouine3m.tif
magick Tataouine3m.tif -crop 7200x7200+12000+0 Tataouine3m_cropped.tif
If I load the resulting image, I get this range of values and the hillshading no longer produces sensible results. Also, the values of the Band 1 (gray) range are now different.
Two things have happened. The coordinate system has been lost and the range of values in band1 has changed. Hillshading doesn't work properly, and if I export the layer as a TIFF and open it in Photoshop it is just a uniform black or dark grey. Frigging the levels doesn't do anything.
The question is twofold:
How can I resize and crop a geotiff (using ImageMagick or some other means) and retain the coordinates and height range so that I can generate a hillshade off it?
My google-fu is failing me. Am I barking up the wrong tree here?
