Performance issue

[Fulvio Fulvioni]

Hi,
We are having some trouble opening some .ndpi images in our medical viewer.
We are trying to open a file with the following characteristics:

hamamatsu.AHEX[0]
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[0].fluorescence
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[0].ploidy
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[1]
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[1].fluorescence
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[1].ploidy
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[2]
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[2].fluorescence
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.AHEX[2].ploidy
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
hamamatsu.Created 2019/07/12
hamamatsu.Macro.S/N 000903
hamamatsu.NDP.S/N 000128
hamamatsu.Objective.Lens.Magnificant 35.16
hamamatsu.PSHV 100
hamamatsu.PSHV.10x 100
hamamatsu.PSHV.40x 100
hamamatsu.PSHV.ploidy 100
hamamatsu.PSHV.ploidy.10x 100
hamamatsu.Product C13239-01
hamamatsu.Reference A-220000004-A-01-001
hamamatsu.SourceLens 20
hamamatsu.Updated 2021/01/18
hamamatsu.XOffsetFromSlideCentre 5617940
hamamatsu.YOffsetFromSlideCentre -727733
hamamatsu.YRNP[0] 0,0,0,0
hamamatsu.YRNP[1] 0,0,0,0
hamamatsu.YRNP[2] 0,0,0,0
hamamatsu.calibration.version 3519
hamamatsu.ccd.height 0
hamamatsu.ccd.width 8449
hamamatsu.ccd.width.ploidy 8449
hamamatsu.coarse.focus.pitch 10000
hamamatsu.colorfilterID 0
hamamatsu.cube.kind 0
hamamatsu.exposure.barcode.macro 740
hamamatsu.exposure.slide.darkfield.macro 10
hamamatsu.exposure.slide.macro 20
hamamatsu.fine.focus.pitch 250
hamamatsu.focalplane.leftbottom 88914,689278,87825
hamamatsu.focalplane.lefttop 88914,489278,88404
hamamatsu.focalplane.rightbottom 488914,689278,86827
hamamatsu.focalplane.righttop 488914,489278,87429
hamamatsu.lane.shift.amount -1
hamamatsu.roi.barcode.macro 948,253,1272,672
hamamatsu.roi.slide.macro 59,257,1264,668
hamamatsu.slant.leftbottom 0,0,0
hamamatsu.slant.lefttop 0,0,0
hamamatsu.slant.rightbottom 0,0,0
hamamatsu.slant.righttop 0,0,0
hamamatsu.slide.tickness 0
hamamatsu.stage.center 178914,589278
hamamatsu.system.version 1.0
hamamatsu.target.white.intensity 235
hamamatsu.valid.DDKP 0
hamamatsu.valid.DLTP 0
hamamatsu.valid.DSHP 0
hamamatsu.variable.exposuretime 0
hamamatsu.zCoarse[0] 0,0,0,0
hamamatsu.zCoarse[1] 0,0,0,0
hamamatsu.zCoarse[2] 0,0,0,0
hamamatsu.zFine[0] 0,0,0,0
hamamatsu.zFine[1] 0,0,0,0
hamamatsu.zFine[2] 0,0,0,0
openslide.level-count 8
openslide.level[0].downsample 1
openslide.level[0].height 53504
openslide.level[0].tile-height 8
openslide.level[0].tile-width 1920
openslide.level[0].width 69120
openslide.level[1].downsample 2
openslide.level[1].height 26752
openslide.level[1].tile-height 4
openslide.level[1].tile-width 960
openslide.level[1].width 34560
openslide.level[2].downsample 4
openslide.level[2].height 13376
openslide.level[2].tile-height 8
openslide.level[2].tile-width 480
openslide.level[2].width 17280
openslide.level[3].downsample 8
openslide.level[3].height 6688
openslide.level[3].tile-height 4
openslide.level[3].tile-width 240
openslide.level[3].width 8640
openslide.level[4].downsample 16
openslide.level[4].height 3344
openslide.level[4].tile-height 8
openslide.level[4].tile-width 120
openslide.level[4].width 4320
openslide.level[5].downsample 32
openslide.level[5].height 1672
openslide.level[5].tile-height 4
openslide.level[5].tile-width 60
openslide.level[5].width 2160
openslide.level[6].downsample 64
openslide.level[6].height 836
openslide.level[6].tile-height 2
openslide.level[6].tile-width 30
openslide.level[6].width 1080
openslide.level[7].downsample 128
openslide.level[7].height 418
openslide.level[7].tile-height 1
openslide.level[7].tile-width 15
openslide.level[7].width 540
openslide.mpp-x 0.44006336912515404
openslide.mpp-y 0.44006336912515404
openslide.objective-power 20
openslide.quickhash-1
edd079959828875e175c886ffeb8d11cd2067b744d461333367a6afe4ac8d6df
openslide.vendor hamamatsu
tiff.DateTime 2022:09:21 13:27:41
tiff.Make Hamamatsu
tiff.Model C13239-01
tiff.ResolutionUnit centimeter
tiff.Software NDP.scan 3.3.2
tiff.XResolution 22724
tiff.YResolution 22724

The following is the code we are using to test the performances (using the
openslide java wrapper):
```
File file = new File("C:/path/to/file");
OpenSlide slide = new OpenSlide(file);
long t0 = System.currentTimeMillis();
slide.createThumbnailImage(512);
System.out.println("thumb extracted in: " + (System.currentTimeMillis() -
t0));
```
Trying to compute said thumbnail from a local file on an SSD it takes
around 2 seconds, while accessing it from a remote HDD archive it takes
around 70 seconds. Just as a reference, doing the same test with an .svs it
take at most 700 ms on the remote HDD.

Is this image strange in any way? Is there anything we can do to improve
the reading performance of openslide?

Thanks a lot!
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