.\"
.\" wm_corvi_d.1 - the *roff document processor man page source
.\"
.TH wm_corvi_d 1 "98/07/29" "Watermarking, Version 1.0"
.SH NAME
.B wm_corvi_d
\- a program to extract a signature from the DWT residue of a watermarked
image
.SH SYNOPSIS
.B wm_corvi_d
[
.BI \-a \ number
]
[
.BI \-e \ number
]
[
.BI \-f \ number
]
[
.BI \-F \ ffile
]
[
.BI \-g \ number
]
[
.B \-h
]
[
.BI \-i \ ifile
]
.br
[
.BI \-n \ number
]
[
.BI \-o \ ofile
]
[
.BI \-q \ number
]
[
.BI \-v \ number
]
.BI \-s \ sfile
.I file
.SH DESCRIPTION
.B wm_corvi_d
is a program to extract a signature from the DWT residue of
a watermarked image
.I file.
The
.B cmp_corvi_sig
program is used to test the extracted signature against the original signature.
The input image is in PGM (portable graymap) format.
.PP
If
.I file
or
.I ofile
is not specified, then standard input or standard output is
used.
.PP
.B gen_corvi_sig
is used to generate a signature file,
.B wm_corvi_e
embeds the signature into an image.
.PP
Please refer to Marco Corvi's paper "Wavelet-based image watermarking
for copyright protection", to get an idea about the algorithm.
.PP
.SH OPTIONS
.TP
.BI \-a \ number
Alpha factor that determines embedding strength of the signature.
Allows to override the setting in the signature file.
.TP
.BI \-e \ number
Wavelet filtering method for forward transformation.
Allows to override the setting in the signature file.
.TP
.BI \-f \ number
Wavelet filter number.
Allows to override the setting in the signature file.
.TP
.BI \-F \ ffile
Wavelet filter definition file.
Allows to override the setting in the signature file.
.TP
.BI \-g \ number
Wavelet filtering method for inverse transformation.
Allows to override the setting in the signature file.
.TP
.B \-h
Print a help message.
.TP
.BI \-i \ ifile
The original image.
.TP
.BI \-o \ ofile
Output watermarked image to the specified
.I file
instead of standard output.
.TP
.BI \-q \ number
Set quantization/quality factor. Overrides the setting in the signature
file.
.TP
.BI \-v \ number
Verbosity level. Default value: 0.
.TP
.BI \-s \ sfile
The signature file to embed into the input image. See
.B gen_corvi_sig
(1) for a description of the file format. Mandatory parameter.
.IR file
Input image in PGM format to sign (watermark). Default: standard input.
.TP
.I file
The watermarked image in PGM format.
.PP
.SH OUTPUT
The signed (watermarked) image in PGM format is written to standard output
or, optionally, to
.I ofile.
.PP
The output file has the following format:
.TP
.B CVSG
Magic to identify file type.
.TP
.I number
The length of the signature in bits.
.TP
.I number
The alpha factor (embedding strength).
.TP
.I number
The quantization/quality factor.
.TP
.I number
The wavelet forward transform filtering method.
.TP
.I number
The wavelet filter number.
.TP
.I file
The wavelet filter definition file name.
.TP
.I number
The wavelet inverse transform filtering method.
.TP
.I numbers
The actual normal distributed signature values, one per line.
.PP
.SH AUTHOR
Peter Meerwald <pmeerw@cosy.sbg.ac.at>
Email bug reports to pmeerw@cosy.sbg.ac.at.
.SH AVAILABILITY
The most recent released version of
.B wm_corvi_d
is always available
at http://www.cosy.sbg.ac.at/~pmeerw/Watermarking or via anonymous ftp from ftp.cosy.sbg.ac.at in the
directory /pub/people/pmeerw/Watermarking.
.SH "SEE ALSO"
.BR gen_corvi_sig
(1),
.BR wm_corvi_e
(1),
.BR wm_corvi_s
(1), 
.BR cmp_corvi_sig
(1)