Nanozoomer annotation coordinate system to openslide pixels
bgilbert at cs.cmu.edu
Tue Nov 11 01:27:02 EST 2014
On 11/10/2014 10:40 PM, Ahmed Bassiouni wrote:
> There is another tag hamamatsu.stage.center, which I then investigated,
> but it does not look like the correct value to look at
It also doesn't exist in every slide.
> In this way, we need the complete width+length of the whole slide to
> calculate coordinates. This has to be somewhere in the ndpi file itself
> ( I hope).
Older slides don't have a lot of metadata (see CMU-1.ndpi, etc.) and
none of it seems relevant. Perhaps the vendor's software hardcodes the
size of the slide?
> BTW There are also tiff.ResolutionUnit (in my slides it says
> centimeter), tiff.XResolution and tiff.YResolution. Can these tags help?
See my previous email. Those OpenSlide properties refer to level 0 of
the main image, and in fact are used to calculate the openslide.mpp-[xy]
properties. NDPI files do contain X/YResolution tags for the macro
image (you can see this with tiffdump) but when using them to calculate
slide dimensions, the rounding error can be significant.
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