Ulf Dittmer wrote:I can't access the full article, and the abstract only talks about watermarks.
i will upload all abstract please see.
Identification of Reference Color Plane
The pixels of fundus image in the proposed scheme are
given in 24-bits or 3 bytes of RGB color and represented in
TIF (Tagged Image File) format. The fundus camera uses
special green filter for photograph the fundus area. Thus, the
green channel of the fundus image will contain the important
details than other color channels. Hence, the green color plane
is chosen as reference color plane to generate the watermark.
It can also be done according to the color characteristics for
other medical imaging modalities such as X-Ray, CT, MRI,
SPECT and PET.
Messy system is a dynamical system whose behavior
changes with time. These changes are very sensitive to the
initial conditions. This sensitivity manifests changes as an
exponential growth of perturbations in the initial conditions.
Thus, the behavior of messy system appears to be random,
though they are deterministic. The dynamic changes of this
system are completely defined by their initial conditions
without any random elements. Therefore, the watermark is
generated through messy system using the reference color
plane as initial condition. Thereby, the watermark is generated
dynamically. A general messy system is defined by the
following equation
Xn+1=f(n)
Where f(*) refers the iterative, non linear function. It
iteratively produces the values for initial value. It is known as
messy sequence. The iteration will be stopped, when the
parameters in f(*) satisfy a certain requirements for messy
status. Once the sequence reached the messy status, it can be
used to generate the watermark.
In the proposed system, a hybrid optical bi stable messy
system [23] is used which is defined by
f(xn) = 4 sin 2 (Xn - 2.5) (2)
The watermark is generated through messy system by
using prominent pixel values of reference color plane of the
image as seed. The initial values to the messy system is
designed by
c sec/k,O)=a* jlo01(s(k)li)*i +b* pos+c*key (3)
Where, s(k) refers the pixel values of reference color
plane of the image. a, band c are predefined constants and I refers embedding depth. The position information (pas) and
secret key (key) is also used in the initial condition. The messy
sequence is generated by substituting c_seg (k, 0) value for Xn
in Eqn.2.For the kth pixel the sequence is referred as
c_seq (k, i), i=l, 2, 3 ... 1 The reasonable number of iteration
(I) is performed for the pixel to attain the messy status.
This sequence contains floating numbers that is converted in
to binary sequence in the proposed scheme. Hence, the
thresholding T is introduced here to convert the sequence
c_seq (k, i) from floating to binary sequence w (k, i). The
w (k, i) is obtained by
{1 c _seq(k,i) w(k,i ) = > T
0 Elsewhere
Embedding by Intra Plane Difference Expanding
The watermark generated in previous stage will be
embedded in this stage by using intra-plane difference
expanding as shown in fig .2. In the embedding stage, the
original image Img (L J, K) is divided into color planes. Here I
denote number of rows, J denotes number of columns and K
denotes number of planes. Since, the input image is in RGB
(Red, Green, Blue) mode, k=3in the proposed scheme. The
green color plane will be used as seed to generate the
watermark in messy system. Since, the watermark is generated
dynamically; it will be unique to the images. Then, pixel pair
is formed from the red and blue color planes of the images. By
checking overflow and underflow condition for pixel pair, the
watermark is embedded in the difference of the pixel pair by
expanding the difference. This is known as intra-plane
difference expanding.
Integer Transform: For a 8 bit gray scale pixel pair (x,
y), 0::; x,y ::; 255, the integer transform is given by the pair
(m, d).Where m refers integer average and drefers differenceWhere L J refers floor operation which rounds the value
to nearest integer. In the integer transform, the difference (d)
is modified based on the watermark bit (bit) to hide the bit into
the pixel pair. The modification of difference (d ') is given by
d'
= 2 * d + bit (9)
The modification process checks two conditions. They
are overflow and underflow. It is done to ensure that the
difference is expandable or not. The expandable difference
should satisfy the following condition.
Id' i 2 * (255 - m) if128 m 255
(10)
Id' I2*m+l ifOm127
Only expandable difference can be used for embedding. If
all the expandable differences are used, the capacity will reach
its limit. Let N and Ne denote the number of differences and
the number of expandable differences, respectively. The
hiding capacity of an image is defined as:
Ne
C= - (11)
N
The difference can be expanded in multilayer also. It
means that the same pixel pairs are selected for further data
embedding. Here some of the differences may not be
expandable for longer time [24].
In the proposed scheme, the pixel pairs are formed from
red and blue color plane's pixel values. This is known as intra
plane difference expanding. Thus, the difference between the
pixels from different (Red and Blue) color planes is expanded
for embedding watermark in the proposed scheme. Thereby,
the watermarked image (Wjmg) is generated for the given
original image (Img).