How to write WIC XMP people tags to jpg?

Issue

I have images with people tagging information in xml format. I wish to edit this information and also add it to pictures that do not yet have it. By looking at the xml I assume it is based on the people tagging used in the microsoft imaging component.

I haven't quite understood the format, but I understood it sof far, that I can alter or gemerate the xml, I just do not know where to write it in the image. I am probably just doing some stupid mistake, because I am not experienced with these image metadatas. So if you think I'm just on the wrong track and that can be done much simpler, please tell me.

In those images that already contain this xml, I can use search and replace to update the xml. However I have a lot of pictures that do not yet contain that information and I do not know where I should write it to inside the image.

Images that already contain this information can be read with exiftool as follows:

exiftool -xmp -b existingTags.JPG

The result is the following xml:

<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?> <x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP 
Core 4.4.0-Exiv2"> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about="" 
xmlns:xmp="http://ns.adobe.com/xap/1.0/" xmlns:dc="http://purl.org/dc/elements/1.1/" 
xmlns:MP="http://ns.microsoft.com/photo/1.2/" xmlns:MPRI="http://ns.microsoft.com/photo/1.2/t/RegionInfo#" 
xmlns:MPReg="http://ns.microsoft.com/photo/1.2/t/Region#" xmp:Rating="0"> <dc:subject> <rdf:Bag> <rdf:li>Valeriya
</rdf:li> </rdf:Bag> </dc:subject> <MP:RegionInfo rdf:parseType="Resource"> <MPRI:Regions> <rdf:Bag> <rdf:li 
MPReg:Rectangle="0.48, 0.418, 0.059333, 0.089" MPReg:PersonDisplayName="findus_l"/> </rdf:Bag> </MPRI:Regions> 
</MP:RegionInfo> </rdf:Description> </rdf:RDF> </x:xmpmeta> <?xpacket end="w"?>

However I cannot write the information using exiftool. When I ran this command, it simply reads the information again, instead of writing the contents of the file to the image:

exiftool -xmp<=alteredXMP.txt existingTags.JPG

A bit of research has shown me, that exiftool can only write specific xmp tags, and the people tagging tags from windows imaging component do not seem to be part of this.

Where in the image file should I write the information? Can I somehow find this spot programmatically and then just insert the xml there?

I am using Kotlin as programming language but I don't mind having to call command line functions or other programs.

Background: I have a Synology Diskstation and use the included software called photo station. The photo station supports tagging of people on the images and uses this given format. I like the photo station in many ways, but the face recognition is bad, so I want to use my own but have photo station be able to read it.

Solution

The data you are trying to write is part of the Microsoft Region Structure. XMP Structured data is a complex subject but you should be able to add the data with exiftool by writing region names to the RegionPersonDisplayName tag and the region dimensions to the RegionRectangle. Using the data in your example, the command would be:
exiftool -RegionPersonDisplayName=findus_l -RegionRectangle="0.48, 0.418, 0.059333, 0.089" /path/to/files

If you have to write multiple regions, you can just add them on, but you must keep names and the matching dimensions in the same order. For example
exiftool -RegionPersonDisplayName=findus_l -RegionRectangle="0.48, 0.418, 0.059333, 0.089" -RegionPersonDisplayName="John Smith" -RegionRectangle="0.37645533, 0.04499886, 0.35111009, 0.26633097" /path/to/files

These commands would overwrite any existing region data. If you are adding new names without overwriting, you would change the equal signs to PlusEqual +=.

Answered By - StarGeek