AIPS HELP file for IMTXT in 31DEC22
As of Tue Nov 28 22:48:55 2023
IMTXT: Write an image to an external text file.
INNAME Input image name (name)
INCLASS Input image name (class)
INSEQ -1.0 9999.0 Input image name (seq. #)
INDISK 0.0 9.0 Input image disk unit #.
BLC 0.0 4096.0 Bottom left corner of image
TRC 0.0 4096.0 Top right corner of image
FACTOR Multiplication factor. 0 => 1
TRANSCOD Fortran format (e.g. 'F5.1')
X Value of blanked pixel.
DATAOUT Output file name (Non-AIPS)
Task: Write an image to an external text file. The format used
is that used by FETCH in reading images.
Each row in the image will be written to a single line in
the output file and there is a limit of 1000 characters
in a line in the output file
INNAME.....Input image name (name). Standard behavior
INCLASS....Input image name (class). Standard defaults.
INSEQ......Input image name (seq. #). 0 => highest.
INDISK.....Disk drive # of input image. 0 => highest number
BLC........The bottom left-hand pixel of the input image
which becomes the bottom left corner of the
subimage. The value (0,0) means (1,1).
TRC........The top right-hand pixel of the input image
which becomes the top right corner of the
subimage. The value (0,0) means take the top
right hand corner of the image.
FACTOR.....The pixel values will be multiplied by FACTOR
before writing. 0 => 1.0
TRANSCOD...The Fortran format to be used. This format should
be appropriate for a single value and will be
replicated as necessary.
NOTE: the format should NOT include the repeat
count, this will be determined from the subimage
size. An example is 'F10.5'.
The appropriate format codes are 'F', 'E' and 'I'.
X..........The value to be used for blanked pixels; this is
the value to be written and is not multiplied by
NOTE: this value must be kept exactly by the
specified format, e.g., don't use -999.99 and
DATAOUT....A file external to the AIPS system into which the
image is to be written.
IMTXT: Task writes an AIPS image to an external, formatted
DOCUMENTOR: W. D. Cotton, NRAO.
RELATED PORGRAMS: FETCH
IMTXT converts a subimage of an AIPS image to an external
text file. This file contains the information in a form that
can be read by task FETCH. The pixel values are encoded one line
per row in the image after possibly scaling using a specified
Fortran format (TRANSCODE). Blanked pixels will be replaced by
a specified value. All data from a row in the selected subimage
must fit in a single line in the output image which may not
exceed 1000 characters.
The output file begins with a small amount of descriptive
information. This is described below.
The user must specify a text file for the image.
The header section of the output file contains a series of
keyword-value pairs to define the image followed by the data in
row order. The output file can be specified as follows shown in
the following example:
where MYAREA is an environment variable set before
starting AIPS e.g.:
percentsetenv MYAREA /mnt/username
Note also: in UNIX all files whose names are passed
to AIPS should have names containing only upper case
The header portion of the image file contains a number of
NAXIS = n (The number of axes in the image, up to
7 are allowed)
DIM = m1, m2, ... (The dimension of each axis used.)
FORMAT = 'r?w.d' (The FORTRAN format used to encode the
pixel values; derived from TRANSCODE.
OBJECT = 'name' (The name of the object)
TELESCOP = 'name' (The name of the telescope used)
INSTRUME ='name' (The instrument used)
OBSERVER='name' (The observers name)
UNITS = 'units' (The units of the image)
EPOCH = xxxx.x (The mean Epoch of the coordinates)
CRTYPE='a','b'... (The axis type (label) of each axis)
CRVAL = x.x, y.y... (The coordinate values at the reference
pixel on each axis, angles are in
CRINC = x.x, y.y ...(The increment in coordinate values
between successive pixels. )
CRREF = x.x, y.y... (The reference pixel on each axis, need
not be an integer.)
CRROT = x.x, y.y... (The rotation; by convention the
rotation angle on the sky is
associated with the declination or
SCALE = x.x (A scale factor to be applied to the
OFFSET = y.y (An offset to be added to the values
read after any scaling.)
BLANK = b.b The blanked (undefined) value BEFORE
any scaling and offset.
The header section is terminated by a '/'. Following this is
the data stored by row (first axis) with the other axes given
with the lower numbered axes varying the fastest.
Most possible errors have more-or-less explanatory messages.
However, if either a scaled pixel value blows the format or a
line exceeds the maximum number (1000) of characters then the
message: "ERROR WRITING OUTPUT TEXT LINE" will be issued and the
task will die.