AW: Re: Questions about tile-serving

Benjamin Gilbert bgilbert at
Thu Sep 3 01:30:18 EDT 2015

On 09/02/2015 04:42 PM, Dr. M. Weihrauch wrote:
> If the openslide zoomlevel is eg only 2px bigger than the openslide
> level, where do you set the cut off not to take the bigger openslide
> zoom level?

The Deep Zoom implementation in OpenSlide Python never upsamples.  For 
example, CMU-1.svs has these downsample values:

Level	Downsample
0	1
1	4.0001215362177929
2	16.000486144871171

When OpenSlide Python is rendering the Deep Zoom level with downsample 
16, it will read pixels from slide level 1 and scale them.  That is 
probably more cautious than necessary, and will have a negative impact 
on performance.  However, I don't have a recommendation for how much 
upsampling to allow.  Does anyone else have experience with this?

--Benjamin Gilbert

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