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Figure (4.3) depicts the processed images for stego-image “Mandrill”
(Figures 4.3(a), (b), and (c)) and retrieved secret image “Lena” (Figures
4.3(d), (e), and (f)) according to Table (4.3). We observe from Figures
4.3(c) and (f) that the best results are obtained when
j
= 9, where
j
repre-
sents the number of bits resolution of the image to hide. It is observed that
when
j
is gradually increased, the quality image is signifi cantly improved.
From Figure 4.3(d-f), one can see that when the value of proposed scal-
ing factor increases the subjective quality of images increases too, it is
observed that Figures 4.3(a-c) have in the upper part a certain lineal dis-
tortion, which can be interpreted as external information inserted to the
cover image. As
j
takes the value of 10 or 24 of this lineal distortion in the
top of the stego-image not easily identifi ed visually. We also present the
wrong images.
FIGURE 4.3
Visual results for different values of
j
in the scaling factor, (a) and (d)
column with
j
= 2, (b) and (e) column with
j
= 5, and (c) and (f)
j
= 9.
More tests were performed to increase the value of
j
to
j
= 24, where
amount is determined by the image type here manipulated. Those signifi -
cant changes of stego-image and the recovered image are observed. Figure
(4.4) presents the visual results for
j
= 10. The proposed scaling factor
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