What is the bug or the crash?
Hi, I tried to export 32 bit height images from the Singleband Gray shader via a pyton script. I can export an image in 32 bit but the height data values stored in it are always reduced to 16 bit values. I expected them to be 32 bit. Is this by design or a bug? Is it possible to change the shader to create 32 bit values?
I calculated a normal map from the exported 32 bit image and always got terracing effects in the normal map - which is a hint to a 16 bit reduction of the data (see image below).
My workaround for this export issue is to create 3 Hillshade renderers (here we only need save 8 bit per channel) to create the normal map manually. But this is uncomftable because the Hillshade shader is creating some errors. Looks like the shader is subtiling the pixels (Resolution per tile is 4096x4096) at 2000 x 2000 pixels per tiles. Those lines are only to be seen when saving the image - on screen there is everything clear (seems to be a post effect hiding the lines). So this is the second bug I found with my workaround workflow.
Thanks for your reply & kind regards.
Steps to reproduce the issue
Save 32 bit image problem:
- Load an 32 bit height image
- chose SingleBand Gray Shader in Layer Styling
- Run the script to save the 32 bit image
Resulting image contains only 16 bit height data in an 32 bit image file.
saveImageScript.txt
Hillshade Problem:
- create an Hillshde of 32 bit height data (bigger than 2000 x 2000 Pixels)
- set Altitude to 0, Azimuth to 0
- choose fitting z-factor
- save the image with the script above or use the export image function for the layer
There shold be black lines all 2000 pixels.
Versions
tested with 3.44.5-Solothurn and 3.32.0 Lima
| QGIS version | 3.44.5-Solothurn |
| QGIS code revision | 5c593399236 |
| |
| Libraries |
| Qt version | 6.8.1 |
| Python version | 3.12.12 |
| GDAL version | 3.12.0 — Chicoutimi |
| PROJ version | 9.7.0 |
| EPSG Registry database version | v12.022 (2025-08-30) |
| GEOS version | 3.13.1-CAPI-1.19.2 |
| SQLite version | 3.50.4 |
| PDAL version | 2.9.0 |
| PostgreSQL client version | 17.3 |
| SpatiaLite version | 5.1.0 |
| QWT version | 6.3.0 |
| QScintilla2 version | 2.14.1 |
| OS version | Windows 10 Version 22H2 |
| |
| Active Python plugins |
| processing_saga_nextgen | 1.1.0 |
| db_manager | 0.1.20 |
| grassprovider | 2.12.99 |
| MetaSearch | 0.3.6 |
| processing | 2.12.99 |
Supported QGIS version
New profile
Additional context
No response
What is the bug or the crash?
Hi, I tried to export 32 bit height images from the Singleband Gray shader via a pyton script. I can export an image in 32 bit but the height data values stored in it are always reduced to 16 bit values. I expected them to be 32 bit. Is this by design or a bug? Is it possible to change the shader to create 32 bit values?
I calculated a normal map from the exported 32 bit image and always got terracing effects in the normal map - which is a hint to a 16 bit reduction of the data (see image below).
My workaround for this export issue is to create 3 Hillshade renderers (here we only need save 8 bit per channel) to create the normal map manually. But this is uncomftable because the Hillshade shader is creating some errors. Looks like the shader is subtiling the pixels (Resolution per tile is 4096x4096) at 2000 x 2000 pixels per tiles. Those lines are only to be seen when saving the image - on screen there is everything clear (seems to be a post effect hiding the lines). So this is the second bug I found with my workaround workflow.
Thanks for your reply & kind regards.
Steps to reproduce the issue
Save 32 bit image problem:
Resulting image contains only 16 bit height data in an 32 bit image file.
saveImageScript.txt
Hillshade Problem:
There shold be black lines all 2000 pixels.
Versions
tested with 3.44.5-Solothurn and 3.32.0 Lima
Supported QGIS version
New profile
Additional context
No response