Content-type: text/html Manpage of imgen

imgen

Section: User Commands (1)
Index Return to Main Contents
 

NAME

imgen - All-purpose image manipulator/creator  

PERSON RESPONSIBLE

rjs  

CATEGORIES

utility, map manipulation  

DESCRIPTION

IMGEN is a MIRIAD task which modifies an image, or creates a new image. See also maths to create images based on expressions involving X, Y and Z.  

PARAMETERS

in
The input image, which is to be modified. The default is a map with one plane which consists entirely of zeros.
out
The name of the output image. No default. The output image has the same characteristics as the input image, if present. If no input image is given, the `imsize', `cell' and `radec' keywords give the characteristics of the output.
factor
Factor to multiply the input image by. This is meaningless if no input image is given. The default is 1.
object
This determines the type of objects added to the input image. Several objects can be given (the objects can be the same type, or different), and minimum match is supported. Possible objects are:
   level      An offset (DC) level.
   noise      Noise (gaussian distribution).
   point      A point source.
   gaussian   An elliptical or circular gaussian.
   gauss3     3D elliptical or circular gaussian (for cubes).
   disk       An elliptical or circular disk.
   j1x        J1(x)/x function
   jet        Jet model with power law brightness.
   shell      2D projection of an optically-thin spherical shell
   comet      2D projection of a parent molecule in comet.
   cluster    standard isothermal 2D projection for cluster gas.
   powerlaw   standard power-law model
   j0         J0 Bessel function for holography work
spar
Parameters which give the characteristics of the object. The parameters are given as a sequence of values, with one to six values needed per object (depending on the object type). When there are multiple objects, the parameter value for the second object follow those for the first object, etc. The values are as follows:
  Object Type           SPAR values
  -----------           -----------
   level                  offset
   noise                  rms
   point                  amp,x,y
   gaussian               amp,x,y,bmaj,bmin,pa
   gauss3                 amp,x,y,z,bmaj,bmin,pa,bz
   disk                   amp,x,y,bmaj,bmin,pa
   j1x                    amp,x,y,bmaj,bmin,pa
   jet                    amp,x,y,bmaj,bmin,pa
   shell                  amp,x,y,bmaj
   comet                  amp,x,y,scalelength
   cluster                amp,x,y,core radius 
   powerlaw               amp,x,y,r_1,index1
   j0                     amp,x,y,r_1

Here "offset" is the offset level, "rms" is the rms value of the noise, "amp" is the normally peak value of the object (but see options=totflux below), "x" and "y" are the offset positions (in arcsec) of the object relative to the reference pixel, "z" is the absolute pixel position on the third axis, "bmaj" and "bmin" are the major and minor axes FWHM (in arcsec), "pa" is the position angle of the major axis (in degrees), and "bz" is the FWHM (in pixels) in the 3rd dimension. The position angle is measured from north towards east. The default is an object of unit amplitude, at the reference pixel, with a FWHM of 5 arcsec in x and y and 5 pixels in z. For powerlaw the scale length defaults to 5 arcsec as well and the power-law index defaults to 1. For j0, the default scale length is 5 arcseconds although significant image manipulation after-the-fact is necessary to make this object useful for holography. Comet scalelength, and cluster core radius are in arcsec units. Jet model has brightness with power law index bmaj and bmin along major and minor axes.

imsize
If not input image is given, then this determines the size, in pixels, of the output image. Either one or two numbers can be given. If only one number is given, then the output is square. For testing purposes a third number can be given to create a cube, no good coordinate headers however are written for such cubes. The default is 256 pixels square.
cell
The increment between pixels, in arcseconds. This is only used if there is no input map. The default is 1 arcsec.
radec
If no input image is given, this gives the RA and DEC of the image, in hours and degrees, respectively. They can be given in hh:mm:ss,dd:mm:ss, or as decimal hours and degrees. The default is RA=0, DEC=30.
options
Extra processing options. Several can be given, separated by commas. Minimum match is used. Possible values are:
  totflux  Interpret the "amp" values in the spar keyword as
           total integrated flux densities (Normally the "amp"
           parameters are interpretted as peak values).
seed
Number used to initialise the random number generator. This is an integer. Invoking IMGEN with the same value of SEED will give you identical instance of the noise, whereas a different value will give you a different instance.


 

Index

NAME
PERSON RESPONSIBLE
CATEGORIES
DESCRIPTION
PARAMETERS

This document was created by man2html, using the manual pages.
Time: 18:35:38 GMT, July 05, 2011