Determining the actual scale factor ...

Hauke Heibel hauke.heibel at
Wed Dec 1 10:55:40 EST 2010

Thank you for reminding me of that page, Jan. It looks quite promising
and the big question is how we can confirm the parameter meaning for
Aperio and Hamamatsu. Are the testing files we have for Aperio and
Hamamatsu enough as a verification? Would it alternatively be fine to
implement the functionality for Aperio and Hamamatsu and implement the
error handling as done for openslide_get_layer_downsample where a -1.0
is returned in case of failure, i.e. unknown property?

- Hauke

On Wed, Dec 1, 2010 at 4:43 PM, Jan Harkes <jaharkes at> wrote:
> On 12/01/2010 10:30 AM, Hauke Heibel wrote:
>> I am wondering whether you know if there is a way to determine the
>> actual scale at which an image was taken. It is not uncommon in
>> microscopy applications to offer 1x 2x 5x ... 40x zoom settings
>> corresponding the standard magnification lenses. In the MIRAX format
>> there is a tag called OBJECTIVE_MAGNIFICATION which seems to state the
>> zooming factor at which the zero-th pyramid level was acquired. This
>> is quite nice since it would allow users to implement exactly the
>> aforementioned functionality.
>> I browsed a bit through the TIFF specs but did not find anything
>> corresponding which were jumping right to my eyes. I am just asking
>> since it makes very little sense for me to implement such a function
>> for MIRAX only when there is no way to achieve the same with other
>> image formats.
>> So, in case anybody has an idea and is willing to share it, I would be
>> happy to hear about it.
> The following page seems relevant. It looks like Adam already tried to
> identify possibly relevant properties in different slide formats
> supported by openslide.
> Jan
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