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NAME

       vsynth - synthesize an image

SYNOPSIS

       vsynth -pattern pattern [-option ...] [outfile]

DESCRIPTION

       vsynth  creates  a one-band image with a specified size, pixel representation, and pattern
       of pixel values.

       The program knows how to create several different types of patterns. These  are  described
       below under PATTERNS.

COMMAND LINE OPTIONS

       vsynth accepts the following options in addition to those described below under PATTERNS.

       -help          Prints a message describing options.

       -out outfile   Specifies  where  the  synthesized  image  is to be written as a Vista data
                      file.

       -pattern pattern
                      Specifies, with one of the keywords listed below, the type of pattern to be
                      used to set pixel values.

       -nrows nrows and -ncolumns ncolumns
                      Specify the size of the synthesized image. Default: 256 rows and columns.

       -repn bit | ubyte | sbyte | short | long | float | double
                      Specifies  the  pixel  representation  of  the synthesized image.  Default:
                      float.

       -name name     Specifies the name to be given the synthesized image. Default: ``image''.

       The output file can be specified on the command line or allowed to default to the standard
       output stream.

PATTERNS

       The -pattern option specifies which of the following patterns is used to initialized pixel
       values. For each type of pattern there are additional options that may be used to  specify
       pattern  parameters.  In  general,  numeric  parameters are not restricted to just integer
       values.

   Constant
        -pattern constant
       [-base b]                 Default: 0.

              All pixel values are set to b.

   Impulse
        -pattern impulse
       [-amplitude a]            Default: 1.
       [-base b]                 Default: 0.
       [-origin i j]             Default: image center.

              The pixel at row i, column j is set to a; all others are set to b.  (i  and  j  are
              truncated to integers.)

   Ramp
        -pattern ramp
       [-amplitude a]            Default: 1.
       [-base b]                 Default: 0.
       [-origin i j]             Default: image center.
       [-orientation d]          Default: 0.

              The  image  is  filled  with  a  ramp whose slope is a units per pixel. The ramp is
              centered at row i, column j, where it has the value b. The ramp  increases  in  the
              direction  d,  which  is  measured  CCW in degrees from the direction of increasing
              column number.

   Sine Grating
        -pattern sine
       [-amplitude a]            Default: 1.
       [-base b]                 Default: 0.
       [-origin i j]             Default: image center.
       [-phase w]                Default: 0.
           and one of
               [-frequency f]    Default: 0.
               [-orientation d]  Default: 0.
           or
               [-period t]       Default: 8.
               [-orientation d]  Default: 0.
           or
               [-xfreq x]        Default: 0.
               [-yfreq y]        Default: 0.

              The image is filled with a sine grating. The grating has a DC component of b and an
              amplitude  of  a (or 2a peak-to-peak). Its frequency and direction may be specified
              by any of three combinations of frequency (in cycles per pixel, measured either  in
              the  direction of the grating or as horizontal and vertical components), period (in
              pixels per cycle), and orientation (in degrees CCW from the direction of increasing
              column  number).   The  grating  is shifted so that at row i, column j it has phase
              w radians.

   Zone Plate
        -pattern zone
       [-amplitude a]            Default: 1.
       [-base b]                 Default: 0.
       [-origin i j]             Default: image center.
       [-period t]               Default: 8.
       [-phase w]                Default: 0.

              The image is filled with the  zone  plate  pattern  defined  by  f(r) = a cos(r^2/t
              + w) + b, where r is the radial distance from the origin at row i, column j.

   Uniformly Distributed Noise
        -pattern uniform
       [-amplitude a]            Default: 1.
       [-base b]                 Default: 1.
       [-seed s]                 Default: a random number.

              Pixels  are  set  to  random values drawn independently from [b,b+a] according to a
              uniform distribution.  The random number generator is initialized with the seed s.

   Normally Distributed Noise
        -pattern normal
       [-amplitude a]            Default: 1.
       [-base b]                 Default: 1.
       [-seed s]                 Default: a random number.

              Pixel values are set to random values drawn independently  according  to  a  normal
              (Gaussian)  distribution  with  mean  b and standard deviation a. The random number
              generator is initialized with the seed s.

   Binomially Distributed Noise
        -pattern binomial
       [-amplitude a]            Default: 1.
       [-base b]                 Default: 1.
       [-density p]              Default: 0.5.
       [-seed s]                 Default: a random number.

              Pixel values are drawn at random from a binomial distribution. A pixel is given the
              value b with probability 1 -p, and it is given the value b+a with probability p.

SEE ALSO

       VImage(3Vi), Vista(7Vi)

AUTHOR

       Art Pope <pope@cs.ubc.ca>