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.
-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>