Cryptography Reference
In-Depth Information
On the other hand, if a bit information 0 is embedded,
• the average yellow in left block is adjusted to become smaller than that in
right block.
The major merit of this method is that the watermarked image is barely
perceptible to human eyes. When the image contains fewer yellow components,
the performance of this method will be impaired.
Fig. 10.10.
An example of watermarking pattern generated in yellow color.
10.5.6 Special Design Methods
The watermark generated in special designs is a method that generates the
watermark patterns using some special designs. It then adds the watermark
patterns into an image in the spatial domain. Fig. 10.11 shows an example of
watermarking patterns using a design shown in the right hand side. A similar
method was proposed by a company in Japan. The major merit of this method
is the robustness of pattern designs. As shown in Fig. 10.11, the drawback of
this method is it can be easily seen in designed patterns. This is despite the
fact that the patterns are designed to be as beautiful as possible.
10.5.7 Watermark Decoding
We know that in a watermarking technique, the watermark robustness is gen-
erally determined in watermark encoding process. The problem is how to
extract the watermark from a watermarked image effectively. This is the work
of watermark decoding. The embedded watermark must be detected from the
image, which may be geometrically transformed with some image editing or
image processing.
Currently, there are two kinds of watermark decoding methods used for
the applications of print-to-web linking technology using the mobile phone
camera. They are as follows:
(1) Decoding in a mobile phone;
