just about anyone can take a photo of anyone in the public arena
This.

Everyone here likely has their image recorded many times a day without even knowing it (whether kilted or not). Security cameras and other means of photography/videography are everywhere. People on the street take pictures of other people all the time. It's perfectly legal and there's not much you can do about it.

Refusing someone's polite request for a photo doesn't do a bit of good. They will in many cases take your picture anyway, without you knowing it.

If you don't want the attention of others, it's probably best to just wear trousers. But if you wear a kilt, being photographed comes with the territory.