I can't imagine how a law would be written to handle the issue.
Any thoughts on that? (taking pictures of asses and whatnot)
Seems like all laws dead end at the very difficult to prove intent.. otherwise who is to say that any given photo wasn't taken for sexual gratification?
You can't have authoritarian rules restricting picture taking without having potential negative repercussions and abuse that effects freedom of speech and freedom of the press.
The ones we have now are fine-ish.
1. If you are in an area with no reasonable expectation of privacy, you automatically consent to having your picture taken (or being talked to, or waved at, or any other non-violent human interaction that isn't illegal). However, your image or likeness cannot be used to generate a profit or promote a product or company without written consent.
2. If you are in an area with a reasonable expectation of privacy, you do not automatically consent to having your picture taken. You do not have consent to take a picture of someone in a bathroom, changing room, or in the privacy of a house to which you are not invited.
3. Intent should have little to no say towards the severity of the punishment or severity of the crime. Policing thoughts is bad.
That should be enough. The matters regarding perversion and morality are best left to our society's social structures to handle, not the law. It is not illegal to be a pervert, but it is illegal to commit a perverted action that harms others as a result.
Matters regarding stalking, harassment, patterns of behavior, and threats to the well being of others can be dealt with by any law enforcement or judges handling the case.