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Fitstopnm User Manual(0) Fitstopnm User Manual(0)
NAME
fitstopnm - convert a FITS file into a PNM image
SYNOPSIS
fitstopnm [-image=N] [-scanmax] [-printmax] [-min=f] [-max=f] [-omaxval=N [FITSfile]
Minimum unique abbreviation of option is acceptable. You may use double hyphens instead
of single hyphen to denote options. You may use white space in place of the equals sign
to separate an option name from its value.
DESCRIPTION
This program is part of Netpbm(1).
fitstopnm reads a FITS (Flexible Image Transport System) file as input and produces a PPM
image if the FITS file consists of 3 image planes (NAXIS = 3 and NAXIS3 = 3), or a PGM
image if the FITS file consists of 2 image planes (NAXIS = 2), or if you specify the
-image option.
Note that the PPM image is highly unlikely to be a true PPM image, as it is not normal for
a FITS image to use the third axis as R, G, and B components of the pixels. The most com-
mon interpretation when there are 3 axes is that the third one is time. So the image is
instead a pseudo-PPM in which the three sample values of a pixel represent something other
than color components, for example gray levels at three instants (this variation on PPM is
common in programs such as fitstopnm that predate the PAM format).
If you work with FITS images with 3 axes, you should probably always use the -image option
to avoid getting an unwanted pseudo-PPM image.
The program tells you what kind of PNM image it is writing.
OPTIONS
-image=N
This is for FITS files with three axes. This option says that the third axis is
for multiple images, and the option value N tells which one you want.
-omaxval=N
This is the maxval that the output PNM image is to have.
By default, the maxval is the least possible to retain all the precision of the
FITS input. That means the difference between the highest and lowest sample value
in the input. If the values range from -5 to 100, for example, the default maxval
would be 106 and each PNM sample value would correspond to one FITS sample value.
For a FITS input with floating point sample values, the precision is essentially
unlimited, so this is not possible. In that case, the default maxval is simply
255.
This option was new in Netpbm 10.39 (June 2007). Before that, the output maxval is
always the default.
-min=float
-max=float
You can use these options to override the min and max values as read from the FITS
header or the image data if the header has no DATAMIN and DATAMAX keywords.
-scanmax
Use this option to force the program to scan the data even when the header has
DATAMIN and DATAMAX.
-printmax
With this option, the program just prints the min and max values and quits without
doing its normal job.
This is for use in shell programs. Example:
eval 'fitstopnm -printmax $filename | \
awk {min = $1; max = $2} \
END {print "min=" min; " max=" max}'
NOTES
Pixel Order
You may need to pass the output of fitstopnm through pamflip -topbottom. See pamtofits
<pamtofits.html#pixelorder>
SEE ALSO
pamtofits(1), pamflip(1), pgm(1)
AUTHOR
Copyright (C) 1989 by Jef Poskanzer, with modifications by Daniel Briggs
(dbriggs AT nrao.edu) and Alberto Accomazzi (alberto AT cfa.edu).
DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML source. The master
documentation is at
http://netpbm.sourceforge.net/doc/fitstopnm.html
netpbm documentation 2 August 2015 Fitstopnm User Manual(0)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
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