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
       common 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

       In addition to the options common to all programs based on libnetpbm (most notably -quiet,
       see
        Common  Options  ⟨index.html#commonoptions⟩ ), fitstopnm recognizes the following command
       line 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@nrao.edu) and Alberto Accomazzi (alberto@cfa.harvard.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