If you are in public and someone takes a picture of you and posts it on the web, that is generally fine. You don't have privacy in public. You have a right to privacy in public places where you would expect privacy, i.e. the bathroom. But if you are walking down the street and someone takes a picture, so be it.
If someone takes a photo of you in public and uploads it to the web, that is ok too, as long as they don't use it for commercial purposes. In other words, if someone takes a picture of you eating at Burger King, he cannot then sell that picture to Burger King for use in a Burger King commercial.
If the picture makes you appear to be something you are not, this would be called false light, the person cannot post that. For example, if the person writes that the picture was taken before or after you did something outrageously awful, but you didn't do that thing, that isn't ok.
The picture itself cannot violate law. So if it is taken in a public place, but it is a government facility where pictures cannot be taken, that isn't ok.
You also can't take a picture if it shows private information about someone. I.e. you are walking in or out of a psychiatrist's office.
While I am an attorney, I am not your attorney, nor is this legal advice. It is simply meant to serve as general information. It is not exhaustive and it does not reflect your specific situation, which could easily change the situation. You should not act or refrain from acting based on what I say. You should contact an attorney in your jurisdiction for legal advice.