Regarding aggregation at multiple levels

[Sriram Somanchi]

Thanks Bejamin! 

I will look into VIPS for creating downsampled levels. 

-Sriram

-----Original Message-----
From: Benjamin Gilbert [mailto:bgilbert at cs.cmu.edu] 
Sent: Wednesday, November 07, 2012 3:41 PM
To: Sriram Somanchi
Cc: 'Kent Johnson'; openslide-users at lists.andrew.cmu.edu
Subject: Re: Regarding aggregation at multiple levels

On 11/07/2012 03:18 PM, Sriram Somanchi wrote:
> I understand that it might not have to do with OpenSlide library, 
> however I want to understand how this aggregation is done. I tried 
> this on the sample file that I have downloaded (CMU-1.svs) from 
> openslide webpage and I get the following output.
>
> Like I said it might have to do with the library, however, it will be 
> great if I can directed to documentation about this aggregation over 
> multiple levels.

I'm not aware of any documentation on the scaling algorithms used by the
various scanner software.  However, slide formats typically use lossy
compression, so you may be seeing compression artifacts.

The value of the lower-resolution levels isn't their quality, it's the fact
that they've been precomputed.  If you need to control the quality of the
downsampling, you should regenerate the downsampled levels yourself, e.g. by
using VIPS to create a pyramidal tiled TIFF from slide level 0.

--Benjamin Gilbert