Relation between mpp-{x,y} and {X,Y}Resolution

[Derek Magee]

The logic I use is (pseudocode):

If tiff.ResolutionUnit==”centimetre” : numerator = 10000 // microns in CM
Else : numerator = 25400 // Microns in Inch
// I’m not totally sure what other values there can be (I’ve never seen anything but “centimetre”, and the standard uses numbers*), but assume it’s inches if not cm. Technically there’s
// a third option of “No absolute unit of measurement.”, but rare enough not to worry about IMHO ….

Mppx = numerator / tiff.XResolution
Mppy = numerator / tiff.YResolution

Where tiff.ResolutionUnit, tiff.XResolution, and tiff.YResolution come from openslide. These tags are standard and well documented:

http://www.awaresystems.be/imaging/tiff/tifftags/resolutionunit.html
http://www.awaresystems.be/imaging/tiff/tifftags/xresolution.html
http://www.awaresystems.be/imaging/tiff/tifftags/yresolution.html

HTH

Derek

From: openslide-users [mailto:openslide-users-bounces+d.r.magee=leeds.ac.uk at lists.andrew.cmu.edu] On Behalf Of kyuhyoung choi
Sent: 11 April 2017 16:08
To: openslide-users at lists.andrew.cmu.edu
Subject: Relation between mpp-{x,y} and {X,Y}Resolution

I have many WSIs from 7 different sources (medical centers)
I want to scale the level 0 images of them to a standard resolution (given by me).
So I thinking about using mpp-{x, y} to do that.
However, for some of the slides, I can not access mpp-{x, y} properties when I open them with openslide.
Instead I found I can get the properties of {X, Y}Resolution and ResolutionUnit.
Is there any equation between {X, Y}Resolution and mpp-{x,y} ?
If not, how can I scale all the slides to the same resolution?
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