Combinational image watermarking in the spatial and

							  Combinational image watermarking in the
  spatial and frequency domains


Source: Pattern Recognition, Vol. 36, No. 4, April
         2003, pp. 969-975
Authors: Frank Y. Shih, Scott Y.T. Wu

Speaker: Yu-An Ho
Date: 2004/2/6



                                                     1
Outline
   Introduction
   Flowchart
   The watermarking in the spatial domain
   The watermarking in the frequency domain
   Experimental results
   Random sequence generator
   Conclusions
   Comments
                                               2
Introduction
There are many aspects to be noticed in
Watermarking design:
 Imperceptibility

 Security

 Robustness

 Capacity




                                      3
Flowchart

            DCT
    +




                      IDCT
                  +



                             4
   The watermarking in the spatial
   domain
187 191   10111011 10111111
                              LSB:least significant bits
181 176   10110101 10110000

                               10111011 10111111
                   +
                               10110100 10110001


               1   1                187 191
               0   1
                                    180 177
                                                     5
       The watermarking in the
       frequency domain (1/2)
2*2 Watermark block          8*8 block




                                         Host Image 256*256
      Watermark 64*64                    Total blocks = 32*32
      Total blocks = 32*32




                                                                6
        The watermarking in the
        frequency domain (2/2)
     0 0                  502   22

                      +
     1 1                  -21   48


2*2 Watermark block



      502   22

      -21   49




                                     8*8 block
                                                 7
Experimental results (1/4)




   A 64*64 image is cut from a 128*128 image.
                                                8
Experimental results (2/4)




   A 64*64 image is cut from a 256*256 image.
                                                9
Experimental results (3/4)




       The extracted watermark.
                                  10
   Experimental results (4/4)
Table 1. The comparisons when embedding different
sized watermarks into a Lena image with size 256*256.

                        64*64 128*128 256*256
 PSNR in first step     None 56.58        51.14
 PSNR in second step 64.57 55.93          50.98

 NC                     1      0.9813     0.9644

                                                   11
A 12-bit random sequence
generator



   12 11 10 9   8   7   6   5   4   3   2   1




   12 11 10 8   7   5   4   3   2   1   9   6




                                                12
Flowchart

            DCT
    +




                  +
                      IDCT



                             13
Experimental results




                Cropping half of a Lena image.
 Table 2. Cutting different sizes
Times of 64*64 1         2      3   4   5        6   7   8
NC                0.92 0.88 0.81 0.73 0.68 0.61 0.58 0.52
                                                             14
Conclusions
   The capacity is increased.
   The degree of protection is double.




                                          15
Comments
   Watermark of Gray image.
   Design random sequence generator.




                                        16