[gdal-dev] Extreme time required to create pyramids in MBTiles file (WEBP compression) with large extension but little content

[Michael Otto]

Hello everyone,

I have a few questions about the following procedure.
We use gdal to retrieve raster data for several areas from a WMS and save 
them together in an MBTiles file with a WEBP compression. We then use 
gdaladdo to generate the pyramid levels for the MBTiles file.

Now we have noticed that the larger the boundaries in the MBTiles file, 
the longer it takes to create the pyramids, even if there are only two 
small areas with image tiles.
For example, here are two small areas (EPGS: 25833, in total only 200ha):
BBox1(LowerLeft 251000/5891000, UpperRight 252000/5892000) 
BBox2(LowerLeft 480000/5715000, UpperRight 481000/5716000) 

These times take:
- the determination of the raster data: 8 seconds
- the creation of the MBTiles file: 1 second
- the creation of the pyramids: 16:41 minutes !!!

If such small image areas are close together, the pyramids can be created 
with a snap of the fingers.

Does anyone have any ideas on how to speed up the pyramid creation 
process?
We use gdal 3.8.4.

Best regards.
Michael Otto

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