A Postscript representation of the currently displayed image can be generated using the Print Image option of the File menu. Print Image brings up a dialog box, into which a print directive can be entered. Enter a carriage return in the dialog box or click on the OK button to generate PostScript output. The SAOtng print command works sending the current colormap (as a list of ASCII RGB 3-tuples) and an 8-bit FITS representation of the displayed image (the "scaled" data) to the fits2ps program. This program outputs a PostScript representation of the image to its standard output. The print directive is then used to redirect the PostScript to the appropriate place. Note that fits2ps can be run stand-alone. The command:
cat [foo.fits] | fits2ps -luts [colormap]
will generate a PostScript image from the input FITS file and colormap.
The FITS file must have BITPIX=8, i.e., it must be an 8-bit image.
The print directive allows the PostScript representation of an image to be sent to a variety of places, including printers, disk files, and programs such as ghostview. To send PostScript to a printer, use the directive:
lpr [print options]
e.g.
lpr -Ppscolor
To display the PostScript image in ghostview, use the directive:
ghostview [ghostview options]
If ghostview is specified without any options, the "-" option (take
the input from stdin) is assumed. Otherwise, if you wish to add
options to ghostview, you also must specify the "-" option explicitly:
ghostview -monochrome -
PostScript also can be saved in a disk file by using the print directive:
> [filename]
e.g.
> foo.ps
More generally, the print directive be thought of as the back-end of a Unix
pile-line that is receiving the PostScript image to its standard input.
Thus, any command of the form:
| [Unix command]
or
> [Unix command]
can be used as a print directive. For example, you can print the PostScript
and save it to disk simultaneously with the directive:
| tee foo.ps | lpr -Ppscolor
Note that the "lpr" and "ghostview" directives are handled specially:
the "|" symbol is added automatically as a convenience to the user.
When a file is printed, the print command being used is output to SAOtng's stdout, so that users can verify that the correct operation is being performed.