Create a custom tag that allows multiple values to be add

[AdVanHooft]

I have created the following custom tags
        # TSI tag created by AvH.  PNG:Market
        Market => { },
        # TSI tag created by AvH.  PNG:Option
        Option => { },

I would like to have the same behavior for the Option tag that I created as the Keywords tag has.

With Keywords I can do the following
C:\Users\ad.van.hooft>C:\DEV\exiftool-13.13_64\exiftool-13.13_64\exiftool.exe -Keywords="12345" -Keywords="12346" c:\dev\eprel\eprel408357.png
    1 image files updated

C:\Users\ad.van.hooft>C:\DEV\exiftool-13.13_64\exiftool-13.13_64\exiftool.exe -Keywords+="12347" c:\dev\eprel\eprel408357.png
    1 image files updated

C:\Users\ad.van.hooft>C:\DEV\exiftool-13.13_64\exiftool-13.13_64\exiftool.exe -Keywords c:\dev\eprel\eprel408357.png
Keywords                        : 12345, 12346, 12347

If I do the same thing with my custom field option. I do only get the latest value when I include two entries and with option+ I do get the summation.

So which setting do I need to give my Custom option field?

[StarGeek]

Phil will know for sure, but looking at the PNG tag page, none of them are list type tags. So it may not be possible and you would have to resort to XMP tags.

[Phil Harvey]

Correct.  There is currently no facility for a List-type behaviour of PNG tags.

You would have to store them as a delimited string.

- Phil