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There is a classic channel-capacity notion that exist based on the work of Shannon that gives gives measure of amount of information that can be passed through the channel given its properties.

In the context of watermarking, the image or signal where information is hiding can be thought of as channel. While, in traditional Shannon model the channel distorts the signal if the bandwidth of channel is constrained. Here, if we keep adding more information of the watermark the channel (the host signal) gets distorted.

The question is, is there a notion of what should be the limit or capacity of information (bits) that can be added under a given host image?

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    $\begingroup$ are you asking for a theoretical metric of subjective visual perception? I would say it does not exist. I have seen experiments collecting opinions from volunteers(jpeg, mp3...), but that is far from theory $\endgroup$ – oxuf Jun 23 '17 at 20:23
  • $\begingroup$ Perhaps you'd get an answer if you'd rephrase your question in terms of what amount of modification is tolerable. This has little to do with channel capacity, unless you are completely unconcerned about the effect on the original picture. A 1 Mpixel picture in 8 bit gray scale has 1 Mbyte of information capacity. If you use more than a fraction of that, the original picture will be destroyed. At what exact level it has been compromised is not an absolute thing (depends on the subject of the picture, and the expectations of the observer), so it is not about channel capacity. $\endgroup$ – girolamous Jun 27 '17 at 18:25

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