Skip to content

Support mm10 measurement unit in ALTO upload

The CLI only supports the ALTO uploads if the measurement unit is in pixels.

I want to import BnL documents (https://data.bnl.lu/data/historical-newspapers/) to Arkindex. The annotations are in ALTO/Mets but the measurement unit is in mm10.

I noticed that the height and width in the mets file are in pixels

<mix:imageWidth>2787</mix:imageWidth>
<mix:imageHeight>3839</mix:imageHeight>

and the dpi is given also in the mets file

<mix:xOpticalResolution>300</mix:xOpticalResolution>
<mix:yOpticalResolution>300</mix:yOpticalResolution>
<mix:opticalResolutionUnit>in.</mix:opticalResolutionUnit>

According to this https://www.loc.gov/standards/alto/description.html:

For 1/10mm convert the values into pixel as follows:

pixel = value * resolution / 254

Here is a sample mets file and the corresponding alto file for this image