manual.lyx

包含了多个matlab编程在图像中加入水印的处理代码

gen_cox_sig > cox.sig or 
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gen_cox_sig -o cox.sig
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You can influence e.g.
 the embedding strength that will be used in the embedding step by running
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gen_cox_sig -a 0.5 > too_strong_cox.sig
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Usually, the programs for generating a signature will supply reasonable
 default values for marking a 8-bit gray-scale image of size 
\begin_inset Formula \( 512\times 512. \)
\end_inset 


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Watermark embedding
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Watermark embedding is performed with the following command (for our example,
 we are using Cox' scheme):
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wm_cox_e -s cox.sig -o cox_lena.pgm lena.pgm
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The signature file is parsed to obtain the particular watermark sequence
 and the embedding strength.
 The watermarked image is written to the file 
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cox_lena.pgm
\family default 
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.
 Now it the time to check the perceptual quality of the produced image and
 also have a look at the difference image (see section 
\begin_inset LatexCommand \ref{sec:utility_programs}

\end_inset 

).
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Watermark extraction
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To extract the embedded signature, we execute the command 
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wm_cox_d -s cox.sig -i lena.pgm -o cox.wm cox_lena.pgm 
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Since Cox' algorithm is not blind, the original image is needed as a reference
 to extract the embedded mark.
 The embedded mark will be stored in 
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cox.wm
\family default 
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.
 The original signature, 
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cox.sig
\family default 
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, is used to get the auxiliary embedding parameter correct (e.g.
 embedding strength).
 
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Comparing the mark
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The final step is comparing the original signature against the extracted
 signature.
 The result here is usually a correlation factor.
 Values around 0 indicate that the mark has not been found, values around
 1 
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In most programs a analytical detection threshold for some detection probability
 is not used.
 Hence, one has to observe the output of the detector for many different
 keys (around 1000 I'd suggest) to establish a reasonable threshold for
 detection.
 A good value to go with initially might be 0.2 which means we claim the
 watermark detected if the correlation factor is > 0.2.
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The appropriate command for comparing the mark is
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cmp_cox_sig -s cox.sig cox.wm 
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Batch testing - benchmarking
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If you want to run many test you can pipe the images to be do be watermarked
 (and tested) through the embedder and detector.
 The programs then act like a filter.
 Try something like the following in a Unix shell script:
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gen_cox_sig > cox.sig 
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for i in *.pgm 
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do 
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\SpecialChar ~
\SpecialChar ~
wm_cox_e -s cox.sig $i | 
\backslash 

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\SpecialChar ~
\SpecialChar ~
wm_cox_d -s cox.sig -i $i | 
\backslash 

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\SpecialChar ~
\SpecialChar ~
cmp_cox_sig -s cox.sig 
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done
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\begin_inset LatexCommand \label{sec:recompile}

\end_inset 

Recompiling
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Note, that most watermark embedding/extraction programs use the built-in
 random number generator of the C library, i.e.
 
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srandom()
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 and 
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random().
 
\family default 
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Therefore, if you recompile, chances are that you won't be able to use your
 images watermarked with the previous version.
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The Makefile options for compiling on the different platforms can be found
 in the 
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make/
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 sub-directory of the archive.
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\begin_inset LatexCommand \label{sec:prereq}

\end_inset 

Prerequisites
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NetPBM
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NetPBM is responsible for image file I/O and provides a definition of a
 simple image file format along with many image file format filters that
 allow to convert images to and from NetPBM format.
 
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You need to get and install the NetPBM library at 
\begin_inset LatexCommand \url{http://wuarchive.wustl.edu/graphics/graphics/packages/NetPBM/}

\end_inset 

 or 
\begin_inset LatexCommand \url{http://netpbm.sourceforge.net}

\end_inset 

.
 The library provides 
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pgm.h
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 and the appropriate implementation.
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Unix/Linux platform
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All programs were developed using Linux and GNU C.
 The programs should compile and work with all recent versions of Linux
 and GNU C.
 
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\begin_inset LatexCommand \label{sec:win32_compile}

\end_inset 

Win32 platform
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The programs were ported to the Windows platform using the Cygwin
\begin_float footnote 
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\begin_inset LatexCommand \url{http://www.cygwin.com}

\end_inset 

 
\end_float 
and Mingw
\begin_float footnote 
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\begin_inset LatexCommand \url{http://www.mingw.org}

\end_inset 


\end_float 
 environment.
 Most notable, the file mode for standard input and standard output has
 to be set to binary mode.
 This is accomplished with the 
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setmode()
\family default 
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 or 
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_fsetmode()
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 commands.
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FAQ
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Q: How can I report problems?
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A: See the contact information at the beginning of this document.
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Q: The compiler complains about 
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pgm.h
\family default 
\size default 
?
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A: You need to get and install the NetPBM library, see section 
\begin_inset LatexCommand \ref{sec:prereq}

\end_inset 

.
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Q: What is the best algorithm? 
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A: Depends on your application.
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Q: What is the most robust algorithm?
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A: Depends on the attack.
 See some results on 
\begin_inset LatexCommand \url{http://www.cosy.sbg.ac.at/~pmeerw/Watermarking}

\end_inset 

.
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Q: I need code for a full-frame DCT?
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A: See the files Meerwald/dct.* in the archive.
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Q: I need code for a 8x8 block DCT?
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A: See the files 
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Meerwald/dct.*
\family default 
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 in the archive.
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Q: I need code for the wavelet transform (DWT)?
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A: See the files 
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Meerwald/wavelet.*
\family default 
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 in the archive.
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Q: I get the message 'unable to open filter.dat' - what to do?
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A: Make sure the file filter.dat is in the current directory or accessible
 via path/filename specified in the signature file.
 Use the signature generation command to specify an absolute path if necessary.
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Q: I can't compile the code using some Microsoft product?
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A: Make your life easier, install GNU software! See section 
\begin_inset LatexCommand \ref{sec:recompile}

\end_inset 

.
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Revision history
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version 0.4 (June 21, 2001)
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bug fixes 
\begin_deeper 
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wm_xia_{e|d}.c variable level uninitialized 
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wm_zhu_{e|d}.c variable level uninitialized
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issue with random() vs.
 rand() and RAND_MAX in frid2_common.c
\end_deeper 
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added option to bruyn algorithm to disable block skipping
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added algorithm kim
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version 0.3 (June 18, 2001)
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created a nice (?) manual/documentation
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added algorithms by Dugad, Wang, Zhu, Fridrich
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added Makefiles for Win32 platform (mingw32)
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version 0.2 (February 22, 2001)
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added contribution by Vassilis Fotopoulos (Piva's algorithm,
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DCT, Hartley and subband domain) - see Fotopoulos/ subdirectory
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stuff moved to Meerwald/ subdirectory
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added Bruyndonckx, Corvi, Koch, Xia, Xie algorithms
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version 0.1 (February 18, 2001)
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initial release
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Legal statement
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My license is called "I-don't-care" license: (1) You can do with the accompanyin
g software whatever you want, but don't blame me if it doesn't work or it
 causes damage.
 (2) If you think my work is useful, tell me and tell others, but you are
 not obliged to do so.
 I suggest not to remove information contained in this other documentation
 file.
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\begin_inset LatexCommand \BibTeX[plain]{watermarking}

\end_inset 


\the_end