Re: Re: GD Watermark Question-

On Sep 17, 2010, at 7:36 PM, Ashley Sheridan wrote: > > >>> >>> Even the stenography has its flaws. Opening the image in an image editor, then doing a >>> select all and pasting as a new image would remove any hidden meta info, and saving a couple of >>> times as a jpeg would destroy any detailed information without distorting the photo (assuming it was >>> a photo and not a diagram which would look awful as a jpeg) >>> >>> I'm not sure if you ever had this at your school, but back when I was a kid, once >>> a year class photos would be taken, as well as photos by yourself, even if you didn't want >>> them. To ensure people paid for the proper photo, a large watermark was sprawled across the photo. >>> It took a little while, but with a decent image editor you could pull out that watermark from the >>> scanned in photo and have a good quality photo without paying for it. I'm not saying we should >>> all do this (the photographer needs to be paid somehow!) but I'm saying it's possible if >>> you have the time, inclination and means. >>> >> >> Actually Ash, properly done stenography is actually embedded it the pixels - not the >> metadata and can be placed such that only when the image is reduced to x degraded percent is it lost >> which removes the value of the full res image. >> >> However, the power of real stenography for copyrights (and not for spying) is about the >> fact that the real user uses the image and if it gets copies by someone the stenography copyright >> signatures remain and the copier doesn't know about them >> >> Tom >> >> > > > I know this is getting a little off-topic here, but surely the way a > jpeg destroys data in an image would destroy the stenography information > too? To the human eye all would appear normal, but the copyright info > would be lost? > > I don't know much about this sort of thing, so I'm making assumptions > here. > Totally depends on the approach. Both jpeg and jpeg 2000 have their own mathematical characteristics which can be properly exploited. Nevertheless, I say again the key is to add something is that if an employee of a customer who purchases the image and resells it that you have a possibility to prove. Yes really smart bad people can defeat but 1) most of these aren't stealing your pictures and 2) the others don't know you have embedded a copyright. tom Tom