Is it possible to define the pyramid level count when using tiffsave?

I’m a newcomer to vips / pyvips (and GitHub and Coding for that matter) so please excuse any blatant errors within my question.

I’m working with whole slides images of histopathologic slides and was really happy to find that pyvips can actually write / save such files. Additionally, with pyvips.Image.openslideload one can make use of the OpenSlide library, which we utilize regularly. The problem is, that when I use pyvips.tiffsave and specify pyramid=True it changes the number of levels and I have not found a way out of this. The code I try to test this looks something like this:

import openslide
import pyvips

img_os = openslide.OpenSlide("SomeWSI.svs")
img_pv = pyvips.Image.openslideload("SomeWSI.svs")

save = "Test.svs"
img_pv.tiffsave(save, tile=True, compression='lzw', bigtiff=True, pyramid=True, Q=100)

img_new = openslide.OpenSlide("Test.svs")

print("Saved via pyvips: ", img_new.level_count)
print("Original file: ", img_os.level_count)

and the Output is:

Saved via pyvips:  10
Original file:  3

I’m surely missing something so any help would be much appreciated.

[jcupitt]

By size, I mean number of pixels.

A 50,000 x 50,000 pixel image will have these layers:

0 = 50,000 1 = 25,000 2 = 12,500 3 = 6,250 4 = 3,125 5 = etc.

[jcupitt]

The number of levels created by tiffsave is set by the size of the image. Larger images will need more levels.