[mapserver-users] watermarking

[Thorsten Fischer]

On Thu, 16 Aug 2001, Matt Carlson wrote:

> here's my solution for a baseline copywright embedded on the map using perl
> mapscript.  company-logo points to a pixmap symbol in my markerset file.

There is no reliable way to watermark digital data, though there is
nothing bad in putting a company's logo on a picture.


Watermarking of digital data does not work. Watermarking of digital data
does not work. Watermarking of digital data does not work. No matter what
the manufacturer of your watermarking scheme tells you: it does not work.

At least it does not prevent the copying process itself; if it were
reliable, it would ease tracking of copyright violators, but even that
part ... does not work.

That said: in my humbleth opinion, it's evil. It's digital data, it's in
its nature to be copied.

> what i'm looking for is some way to prevent people from right clicking the
> map gif image on the browser screen and saving the map image onto thier
> desktop.

Hum???

When the image is created (by copying things around and finally creating
a copy to the disk), the webserver copies it to the socket that
belongs to the tcp connection: first copy. Any point inbetween that
routes your packet copies it from one point to another to send it, but I
will skip those here. Then the client takes it and copies it into memory:
second copy. Most probably, it gets cached as well: third copy. I left out
several steps, but the client has several copies already created.

If you do not want your data to be copied, don't copy it yourself and
leave it alone.

> the effect i'm wanting is when someone does save the map image,
> somehow an embedded image shows up with a big copywright message in the
> middle.  i thought company's like digimarc and ewatermark were doing
> something similair to this??

You can do something similar using javascript to trap mouse events and
react according to them. Some porn sites do it, take a look at them. But
you will only shut the most unskilled persons out who cannot turn off
javascript in their browser.


And even if you manage to do this, I can still see the URL of your page
on the top and handcraft a line that I can use with 'wget' or similar
programs, take a look at the html sources and then 'wget' the image by
hand if I really want it. But as it seems to me, the images you are
talking about are not there for being looked at anyway, so I personally
would not bother taking the effort.


Sorry if this sounds like ranting/trolling around, but digital 
watermarking has never worked, it does not work and it will never work;
well, it will maybe work if you blackbox every piece of hard- and software
of every person on earth and seal it shut and then threaten to kill them
if they even think about circumvent the protection.

The logic behind it is flawed. Don't waste your time on it.


hope that helps,

thorsten

--

thorsten fischer : frosch (at) derfrosch (dot) de

hostien in groesseren mengen sind schwer zu beschaffen