Privacy-minded people could print this on a t-shirt.
it doesn't work well at all, but every now and then it produces some pretty amusing results.
Early versions of photoshop would put a big black box over me in some of the photos.
fun for the whole family.
There's a Gibson novel, I think, where the protagonist at some point obtains t-shirts with a pattern which is recognized by the universal DRM-enforcement code in video camera chipsets, making them invisible to surveillance.
But how would they add the watermark? GIMP I guess...
Digital cameras can be pretty sensitive to IR, but there is typically an IR filter over the sensor to prevent detection.
Your best bet is to wear one of these:
https://en.wikipedia.org/wiki/Balaclava_(clothing)#/media/Fi...
Given that it's -10 C outside today... nobody will even think you're weird.