Cryptography Reference
In-Depth Information
The method depicted in Fig. 13.2 is robust. The method proposed in
Fig. 13.3 is appealing from a perceptual point of view. It is however restricted
to lossless environments. To achieve the robustness to high quality JPEG
compression, De Vleeschouwer et al. adopt the method shown in Fig. 13.2,
instead of the method shown in Fig. 13.3. De Vleeschouwer et al.s method
sacrifices the visual quality and suffers from the salt-and-pepper noise in order
to achieve robustness. The watermarked images do not have a high enough
PSNR value. In addition, the e ciency of the retrieved process degrades with
JPEG quality factor. The method is not powerful enough for JPEG2000 com-
pression images. The reason is that JPEG2000 can compress an image with
a very lower quality factor while maintaining the compressed image to a high
quality. Therefore, the De Vleeschouwer et al. method is restricted to JPEG
compression with a high quality factor.
Fig. 13.3. Embedding illustration when restricted by the salt-and-pepper effect.
The pixels in each zone are transformed according to sequence (a) and (b); it impacts
the principal axis orientation.
13.3 Type-II Algorithms
13.3.1 Algorithms Based on Lossless Compression Techniques
Lossless Bit-Plane Compression in the Spatial Domain
Fridrichs group produced profound research on lossless data hiding techniques
and developed a number of algorithms. This group [5] proposed two techniques
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