X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/canny.git/blobdiff_plain/4d8da06dfcc93848b57c76c1b6cff7ca52f0df4a..01ec38902455e4ee4dba09ead751639638481fd2:/intro.tex?ds=sidebyside

diff --git a/intro.tex b/intro.tex
index 28463ee..cd2aeea 100644
--- a/intro.tex
+++ b/intro.tex
@@ -57,7 +57,7 @@ Thus a distortion measure for each
 pixel is individually determined as the sum of the differences between
 the features of the SPAM computed from the cover and from the stego images.
 The features embedded in WOW and UNIWARD are based on Wavelet-based 
-directional filter. Thus, similarelly, the distortion function is 
+directional filter. Thus, similarly, the distortion function is 
 the sum  of the differences between these wavelet coefficients  
 computed from the cover and from the stego images.
 
@@ -66,9 +66,9 @@ Due to this distortion measures, HUGO, WOW and UNIWARD allow
 to embed messages that are $7$ times longer than the former
 ones with the same level of 
 indetectability as LSB matching. 
-However, this improvement is time consuming, mainly due to
+However, this improvement has a larger computation cost, mainly due to
  the distortion function
-computation. 
+calculus. 
 
 
 There remains a large place between random selection of LSB and feature based modification of pixel values.
@@ -108,10 +108,27 @@ One can notice that all the previously referenced
 sche\-mes~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10,DBLP:conf/ih/PevnyFB10}
 produce stego contents 
 by only considering the payload, not the type of image signal: the higher the payload is, 
-the better the approach is said to be. 
-Contrarily, we argue that some images should not be taken as a cover because of the nature of their signals.
-Consider for instance a uniformly black image: a very tiny modification of its pixels can be easily detectable.  
-The approach we propose is thus to provide a self adaptive algorithm with a high payload, which depends on the  cover signal. 
+the better the approach is said to be.
+For instance, studied payloads range from 0.04 to 0.4 modified bits per pixel.
+Contrarily, we argue that some images should not be taken 
+as a cover because of the nature of their signals.
+Consider for instance a uniformly black image: a very tiny modification of its 
+pixels can be easily detectable.
+Practically speaking, if Alice would send
+a hidden message to Bob, she would never consider
+such kind of image and a high embedding rate.   
+The approach we propose here is thus to provide a small complexity 
+self adaptive algorithm
+with an acceptable payload, which 
+depends on the  cover signal. 
+The payload is further said to  
+ be acceptable if it  allows to embed a sufficiently 
+long message in the cover signal. 
+Practically speaking, our approach is efficient enough for
+payloads close to 0.06 bit per pixel which allows to embed 
+messages of length larger than 16000 bits in an 
+image of size $512\times 512$ pixels. 
+
 % Message extraction is achieved by computing the same
 % edge detection pixels set for the cover and the stego image. 
 % The edge detection algorithm is thus not applied  on all the bits of the image,