wtextimage: Convert an IRAF image to a text file

Package: dataio

Usage

wtextimage input output

Parameters

input: An IRAF image file name or template of file names to be converted.

output: Name or root_name of output text file. If more than one IRAF image is being converted, the ordinal of the file in the input file list is appended to output to generate a unique output file name.

header = yes: This parameter determines whether or not a descriptive header precedes the pixels written to the text file. When header = no, only pixels values are converted; no header information is included in the output.

pixels = yes: This parameter determines whether or not to write the pixels to the text file. This can be set to no to only write out the header.

format = "": Output format for each pixel. If not set by the user, the appropriate output pixel format is determined by the image data type. Acceptable formats are chosen from "W.D[defgz]" where w is the field width and d specifies the precision. Fortran formats of the form [iefgz]W.D are also acceptable. If a field width of 0 is specified, (e.g., 0.6g), output will be free format with each output line containing as many pixels as will fit on the line. This is the most space efficient format but requires that the reader program be able to handle free format (list directed) input.

maxlinelen = 80: The maximum number of characters output per line of text; maxlinelen must not exceed 322 characters. (Note that tasks rtextimage and wcardimage cannot read lines of text greater than 161 characters.)

Description

IRAF images are converted to text files with procedure wtextimage. The text file written consists of an optional header optionally followed by the pixel values. The pixels are output in FITS order, that is, the leftmost subscript varies most rapidly. The image header is written in the "keyword = value / comment" format of FITS.

Examples

1. Write a text file from an image section of dev$pix. The default maximum linelength of 80 is used; an output format is specified. The header portion of the output text is as follows:

BITPIX  =                    8  /  8-bit ASCII characters
NAXIS   =                    2  /  Number of Image Dimensions
NAXIS1  =                   10  /  Length of axis
NAXIS2  =                   10  /  Length of axis
ORIGIN  = 'NOAO-IRAF: WTEXTIMAGE'  /
IRAF-MAX=               31431.  /  Max image pixel (out of date)
IRAF-MIN=                  33.  /  Min image pixel (out of date)
IRAF-B/P=                   16  /  Image bits per pixel
IRAFTYPE= 'SHORT INTEGER     '  /  Image datatype
OBJECT  = 'NGC 4147 B 1800   '  /
FILENAME= 'DEV$PIX[1:10,1:10]'  /  IRAF filename
FORMAT  = '11I7              '  /  Text line format
DATA-TYP= '    object (  0 )'   / object,dark,comp,etc.
ITIME   =                 1800  / integration time secs
UT      = '11:23:13'            / universal time
ZD      = '24: 5: 0'            / zenith distance
DATE-OBS= '15/02/1985'          / dd/mm/yy observation
ST      = '13:38:31'            / sidereal time
RA      = '12: 9:20'            / right ascension
DEC     = '18:35:35'            / declination
EPOCH   =                   .0  / epoch of RA and DEC
CAM-TEMP=              -104.95  / camera temperature, deg C
DEW-TEMP=              -192.96  / dewar temp, deg C
HISTORY1= 'bt=   590 bp=     0 cr=     0 dk=     0 '
HISTORY2= 'ff=    55 fg=     0 sc=   .000  bi=   51  '
COMMENT = 'ngc 4147 b 1800'
F1POS   =                    2  / filter bolt I position
F2POS   =                    0  / filter bolt II position
END

2. Write a series of text files from the IRAF images having root name "reduced". One text file is written for each image.

cl> wtext reduced.* txt

Time requirements

It takes almost 10 cpu minutes to convert a 512 square image of real pixels. A 512 square image of integer pixels takes about 3 cpu minutes.