I am trying to understand how to use the symbology options for raster layers in QGIS, particularly the Resampling options, but the official documentation only mentions the setting very briefly and doesn't go into detail about how they work.
I am interested in how to use the settings to best view raster images such as topographic maps or nautical charts, either via tileset map services or offline static formats like GeoTIFF. Most videos and tutorials I can find seem to deal with resampling for data manipulation purposes rather than display purposes.
EDIT: The existing answers about Lanczos resampling are quite informative and will be useful as I go a bit further. However, my question isn't really about different interpolation methods, which I understand fairly well, but rather about what effect the specific settings in QGIS have on rendering the raster layer.
Normally, I would investigate this by changing the settings and visually comparing the result, but I don't see any difference when I apply them (other than the image not rendering at all under certain settings at certain zoom levels). In short, I don't understand from the setting names how I should expect them to affect the image. Specifically:
- What are the "zoomed in" and "zoomed out" settings, and what steps should I take to compare them visually? Are these related to upsampling and downsampling, as described in the Lanczos article?
- What is "oversampling", and how does it affect an image visually?
- Are any of the other symbology settings relevant to the visual appearance of something like a topographic map?