1.1.1.0 image.fromascii

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image.fromascii - Function

1.1.1 Construct a CASA image by conversion from an ascii file
Description

This function is used to convert an ascii disk file to a CASA image file. If outfile is given, the image is written to the specified disk file. If outfile is unset, the Image tool is associated with a temporary image. This temporary image may be in memory or on disk, depending on its size. When you close the Image tool (with the close function) this temporary image is deleted.

You must specify the shape of the image. The image must be stored in the ascii file, one row at a time. This row must be of the correct length and there must be the correct number of rows. For example, let us say the shape of your image is [nx,ny,nz] = [3,4,2], then the image should be stored as

1 1 1                   # row 1; y = 1, z = 1
2 2 2                   # row 2; y = 2, z = 1
3 3 3                   # row 3; y = 3, z = 1
4 4 4                   # row 4; y = 4, z = 1
1.5 1.5 1.5             # row 5; y = 1, z = 2
2.5 2.5 2.5             # row 6; y = 2, z = 2
3.5 3.5 3.5             # row 7; y = 3, z = 2
4.5 4.5 4.5             # row 8; y = 4, z = 2

The Coordinate System, provided as a Coordsys tool converted to a record with coordsys torecord, is optional. If you provide it, it must be dimensionally consistent with the pixels array you give (see also coordsys).

If you don’t provide the Coordinate System (unset), a default Coordinate System is made for you. If linear=F (the default) then it is a standard RA/DEC/Stokes/Spectral Coordinate System depending exactly upon the shape of the pixels array (Stokes axis must be no longer than 4 pixels and you may find the spectral axis coming out before the Stokes axis if say, shape=[64,64,32,4]). Extra dimensions are given linear coordinates. If linear=T then you get a linear Coordinate System.

Arguments


Inputs
outfile	Output image file name. Default is unset.
	allowed:	string
	Default:
infile	Input ascii disk file name. Must be specified..
	allowed:	string
	Default:
shape	Shape of image. Must be specified.
	allowed:	intArray
	Default:	-1
sep	Separator in ascii file. Default is space character.
	allowed:	string
	Default:
csys	Coordinate System record from coordsys torecord(). Default is unset.
	allowed:	any
	Default:	record
linear	Make a linear Coordinate System if csys not given
	allowed:	bool
	Default:	false
overwrite	Overwrite (unprompted) pre-existing output file?
	allowed:	bool
	Default:	false

Returns
bool

Example

The ascii image file shown above can be read as an image this way:

"""
#
print "\t----\t fromascii Ex 1 \t----"
a = [[[ 1. ,  1.5],
      [ 2. ,  2.5],
      [ 3. ,  3.5],
      [ 4. ,  4.5]],
     [[ 1. ,  1.5],
      [ 2. ,  2.5],
      [ 3. ,  3.5],
      [ 4. ,  4.5]],
     [[ 1. ,  1.5],
      [ 2. ,  2.5],
      [ 3. ,  3.5],
      [ 4. ,  4.5]]]
ia.fromarray(’outimage.im’,a,overwrite=true)
ia.toASCII(’myimage.ascii’,overwrite=true)     # write ascii image file
ia.close()                                     # then read ascii image file
ia.fromascii(’myimage.app’, ’myimage.ascii’, shape=[3,4,2], overwrite=true)
ia.toASCII(’myimage2.ascii’,overwrite=true)
ia.close()
#!diff myimage.ascii myimage2.ascii
#
"""

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