Hello, Thank you so much for your time and information.
I know that watermark can spoil photo, but in our kind of business our photos very often are stolen by scammers and used to trick people and steal their money. We offer cottage houses on sea shore for renting here in Ukraine. And quite often scammer use our photos to place ads like private people, that they offer our house for rent at smaller price. People think that they book summer house, but just got money stolen. Such ads in internet live normally not longer then a week. It`s enought time to rip off 5-10 people. Normally they pay 50-60 usd to book house for a week.We normally monitor manually popular local websites to remove such ads as soon as possible. Here is why we need the way quickly prove to marketplace admins that I`m real owner of images.
So, I`m looking for solution to maximize image protection. But, keep image attractive. Thank you for article, this must be good idea to keep transparent image in the middle of image. This would be hard to remove for most scammers (normally they don`t bother with high end retouching, they just use crop and simple tools).