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Pamtofits User Manual(0)                              Pamtofits User Manual(0)



NAME
       pamtofits - convert a Netpbm image into FITS format


SYNOPSIS
       pamtofits [-max f] [-min f] [pamfile]


DESCRIPTION
       This program is part of Netpbm(1).

       pamtofits  reads a PNM or PAM image as input and produces a FITS (Flexible Image Transport System) file as out-
       put.  The resolution of the output file is either 8 bits/pixel, or 16 bits/pixel, depending  on  the  value  of
       maxval  in the input file.  If the input file is a PBM or PGM image, the output file consists of a single plane
       image (NAXIS = 2). If instead the input file is a PPM image, the output file  will  consist  of  a  three-plane
       image (NAXIS = 3, NAXIS3 = 3).


OPTIONS
       -min  and  -max tell pamtofits what 'physical values' zero and maxval sample values, respectively, in the input
       image represent.  Physical values are a FITS concept.  pamtofits sets up the BSCALE and BZERO FITS header cards
       to indicate this information.

       The  default for -min is 0 and for -max is the maxval, which means if you don't specify these options, the FITS
       physical values are in fact the original Netpbm sample values.

       pamtofits always sets up the FITS header DATAMIN and DATAMAX cards to indicate that the highest physical  value
       in the image is the one corresponding to the Netpbm maxval and the lowest is that corresponding to Netpbm zero.
       This isn't really how those cards are supposed to be used, since the input image  doesn't  necessarily  contain
       the full possible range of sample values.  It is a conservative approximation.


NOTES
   Pixel Order
       The  FITS  specification  does not specify which data in the file corresponds to which pixel in the image (i.e.
       which bytes are the the top left pixel, etc.).  Netpbm uses the common sense,  most  popular  arrangement:  row
       major, top to bottom, left to right.  That means in a 10 wide by 20 high image, the first 10 pixels in the file
       are the top row and the last 10 are the bottom row.  Within each row, the first pixel is the leftmost  one  and
       the last pixel is the rightmost one.

       Netpbm  has  always  done  that,  since it first understood the FITS format in 1989, so it is something of a de
       facto standard.  Nobody reported trouble with that until 2008.

       However, at least some versions of ImageMagick and Gimp (as seen in 2008) use bottom to top order,  so  if  you
       use display a FITS image generated by pamtofits, it will appear upside down.  To fix that, use pamflip -topbot-
       tom on the image before feeding it to pamtofits.

       Since 2008, people have noted that NASA distributes FITS files with bottom to top order.



HISTORY
       pamtofits was originally pnmtofits and did not handle PAM input.  It was extended and renamed in  Netpbm  10.30
       (October 2005).

       pnmtofits was itself an extension of pgmtofits, which was added to Pbmplus in 1989.


SEE ALSO
       fitstopnm(1), pam(1) FITS(1)


AUTHOR
       Copyright   (C)   1989  by  Wilson  H.  Bent  (whbAThoh-2.com),  with  modifications  by  Alberto  Accomazzi
       (albertoATcfa.edu).



netpbm documentation           25 September 2005      Pamtofits User Manual(0)