Screenshot Tracking Watermark
color printer contains invisible watermark that has the printer id info.
apparently, screenshot from game WOW, also has invisible watermark that contains your account id, server ip address, timestamp.
apparently, they started doing this in 2007
① Go somewhere where there aren't any (or a lot) of textures. I used the druid blink bug to go to the north end of the world but you should go below Dalaran in Crystalsong Forest, as bluesius suggested, because you will get a better screenshot if you stick your face in the pure white trees.
/console SET screenshotQuality "9"
Make sure you use 9, not 10.
③ Take a few screenshots of the clear, no textures, white area by zooming into a tree and hitting ALT Z, so that your entire screen is white.
④ Open this image in an image editing program like IrfanView (it's freeware), click CTRL+E, select the Sharpening filter, use the highest possible sharpening value (99) and click OK. Now do this two more times, again: CTRL+E, Sharpen 99, OK.
⑤ You are now looking at your character's WoW watermark / custom bar-code / qr code look-a-like / call it what you will:
Apparently, each user has a different set of these repeatable patterns, which contain account and realm information, and it looks like if they are scanned by software that recognizes them, they can reveal our character's account name/id, the time of the screenshot and the the full information of the realm, including its IP address (think “private servers”).
Note that if your screen resolution is too high, the pattern will look something like this:
[2017-07-20 from 〔 Looking inside your screenshots By Sendatsu. At http://www.ownedcore.com/forums/world-of-warcraft/world-of-warcraft-general/375573-looking-inside-your-screenshots.html 〕]
Printer steganography is a type of steganography – “hiding data within data” where tiny yellow dots are added to each page. The dots are barely visible and contain encoded printer serial numbers and timestamps. Unlike many forms of steganography, the hidden information is not intended to be available from a computer file, but to allow serial number and time of printing to be determined by close examination of a printout.
The Electronic Frontier Foundation stated in 2005 that “the documents that we previously received through a (Freedom of Information Request) suggested that all major manufacturers of color laser printers entered a secret agreement with governments to ensure that the output of those printers is forensically traceable….it is probably safest to assume that all modern color laser printers do include some form of tracking information that associates documents with the printer's serial number.”
[2017-07-20 Wikipedia Printer steganography]
What about screenshots from Microsoft Windows, Mac, Android phone, iOS phone?
It's likely that other gaming software also do this.
am not sure if Microsoft Windows, Mac, android phone, iOS, screenshots do this.
The mobile phones could contain very personal info.