Re: [WM]: Query

[madan mohan <madannill@yahoo.co.in>]

hello,
 
To my knowledge, i think watermark need not be present in the entire image can be done in specific region(part of the image) also.
In that case, if some one succeeds in removing the watermark. he can still use the image with out consider damage being done to
it... so it should with stand atleast some minimal amount of attack that wouldnt cause considerable perceptional changes.
 
We generally speak about the tradeoff between robustness and visual perception while embedding  an watermark. The same applies here
too.
 
your watermark can with stand only certain amount of attack which depends on  your level of robustness you acheived (or set) through
your algorithm. Once it exceeds it you land up with an image being corrupted(to an extend which is not useful) carrying no watermark
and no quality. 
 
If any mistake in my reply. please let me and others know too.
 
regards,
Madan
 

 
Vidyasagar Potdar <Vidyasagar.Potdar@cbs.curtin.edu.au> wrote:
Hello
I have a query regarding watermark attacks.

My assumption is that if watermarked images are attacked, and the watermark is successfully removed the quality of the image should
not be changed. 

If the quality of the image is changed then there is no need for an adversary to attack the images because there is no use for
having those modified images. 

Specaially i refer to some attacks that have been listed on some of the benchmarking applications like Checkmark etc.
For example Threshhold, Bending, Warping, Arbitrary Linear Transform, Dithering these attacks change the quality of the image to
such an extent that it could be any useful (my assumption may b i m wrong)

Can anyone comment on these views????
Does a watermarking algorithm really needs to be robust against these attack from a practical point of view???

Thanks very much

Regards

Vidy


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