I'm running the following command to add multiple keywords to an image:
exiftool -keywords+="Flowering" -keywords+="In Flower" -keywords+="Primula vulgaris" -overwrite_original "/pictures/Some Folder/P4130073.JPG"
However, I've noticed that if I do this for an image which already contains a particular keyword, then it'll get added a second time.
How can I ensure that keywords are added only if they're already missing, and that if they exist, it'll do a no-op (and ideally leave the file untouched). I've read a few questions on the forum and the docs, but NoDups docs isn't clear to me (I'm an exiftool n00b) and all the answers I've found only process a single keyword addition.
For an added bonus, if the 'exists' check could be case-insensitive, so much the better (e.g., so that if I'm doing keywords+="Flowering" and the image already has the keyword "flowering", nothing will be done.
I also need this to work on Linux, MacOS and Windows (I know the quotes can complicate things!).
See Exiftool FAQ #17
To prevent duplication when adding new items, specific items can be deleted then added back again in the same command. For example, the following command adds the keywords "one" and "two", ensuring that they are not duplicated if they already existed in the keywords of an image:
exiftool -keywords-=one -keywords+=one -keywords-=two -keywords+=two DIR
The NoDups helper function is used to remove duplicates when they already exist in the file. It isn't used to prevent duplicates from being added in the first place.