[alonfaraj]

What does this PR do?

Whole image read of warped VRT at a different buffer size warps directly at that size with the warp options' resampling, and ignoring the requested eResampleAlg. So reproject ! resize -r average in a pipeline gives a nearest-neighbour result. Use that shortcut only for nearest.

Repro:
(400x400 Byte, 1-pixel 0/200 stripes, EPSG:32631)

gdal raster pipeline read in.tif ! reproject --dst-crs EPSG:3857 ! resize --size 100,100 -r average ! write out.tif

Interior of out.tif:
before min=0 max=200
after min=88 max=111 (same as running reproject and resize separately)

What are related issues/pull requests?

AI tool usage

• AI (Y-a-t-il-un-Copilot-dans-l'avion, Chat-j'ai-pété, Jean-Claude Dusse or something similar) supported my development of this PR. See our policy about AI tool use. Use of AI tools must be indicated.

Tasklist

• Make sure code is correctly formatted (cf pre-commit configuration)
• Add test case(s)
• Add documentation
• Updated Python API documentation (swig/include/python/docs/)
• Review
• Adjust for comments
• All CI builds and checks have passed
• ADD YOUR TASKS HERE

Environment

Provide environment details, if relevant:

• OS: Ubuntu 26.04
• Compiler: gcc (Ubuntu 15.2.0-16ubuntu1) 15.2.0