1Fitstopnm User Manual(0) Fitstopnm User Manual(0)
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6 fitstopnm - convert a FITS file into a PNM image
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10 fitstopnm [-image=N] [-scanmax] [-printmax] [-min=f] [-max=f] [-omax‐
11 val=N [FITSfile]
12 Minimum unique abbreviation of option is acceptable. You may use dou‐
14 ble hyphens instead of single hyphen to denote options. You may use
15 white space in place of the equals sign to separate an option name from
16 its value.
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21 This program is part of Netpbm(1).
22 fitstopnm reads a FITS (Flexible Image Transport System) file as input
24 and produces a PPM image if the FITS file consists of 3 image planes
25 (NAXIS = 3 and NAXIS3 = 3), or a PGM image if the FITS file consists of
26 2 image planes (NAXIS = 2), or if you specify the -image option.
27 Note that the PPM image is highly unlikely to be a true PPM image, as
29 it is not normal for a FITS image to use the third axis as R, G, and B
30 components of the pixels. The most common interpretation when there
31 are 3 axes is that the third one is time. So the image is instead a
32 pseudo-PPM in which the three sample values of a pixel represent some‐
33 thing other than color components, for example gray levels at three
34 instants (this variation on PPM is common in programs such as fitstopnm
35 that predate the PAM format).
36 If you work with FITS images with 3 axes, you should probably always
38 use the -image option to avoid getting an unwanted pseudo-PPM image.
39 The program tells you what kind of PNM image it is writing.
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45 -image=N
46 This is for FITS files with three axes. This option says that
47 the third axis is for multiple images, and the option value N
48 tells which one you want.
49 -omaxval=N
52 This is the maxval that the output PNM image is to have.
54 By default, the maxval is the least possible to retain all the
56 precision of the FITS input. That means the difference between
57 the highest and lowest sample value in the input. If the values
58 range from -5 to 100, for example, the default maxval would be
59 106 and each PNM sample value would correspond to one FITS sam‐
60 ple value.
61 For a FITS input with floating point sample values, the preci‐
63 sion is essentially unlimited, so this is not possible. In that
64 case, the default maxval is simply 255.
65 This option was new in Netpbm 10.39 (June 2007). Before that,
67 the output maxval is always the default.
68 -min=float
71 -max=float
73 You can use these options to override the min and max values as
75 read from the FITS header or the image data if the header has no
76 DATAMIN and DATAMAX keywords.
77 -scanmax
80 Use this option to force the program to scan the data even when
81 the header has DATAMIN and DATAMAX.
82 -printmax
85 With this option, the program just prints the min and max values
86 and quits without doing its normal job.
87 This is for use in shell programs. Example:
89 eval 'fitstopnm -printmax $filename | \
91 awk {min = $1; max = $2} \
92 END {print "min=" min; " max=" max}'
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98 Pixel Order
99 You may need to pass the output of fitstopnm through pamflip -topbot‐
100 tom. See pamtofits ⟨pamtofits.html#pixelorder⟩
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105 pamtofits(1), pamflip(1), pgm(1)
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109 Copyright (C) 1989 by Jef Poskanzer, with modifications by Daniel
110 Briggs (dbriggs@nrao.edu) and Alberto Accomazzi (alberto@cfa.har‐
111 vard.edu).
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114 This manual page was generated by the Netpbm tool 'makeman' from HTML
115 source. The master documentation is at
116 http://netpbm.sourceforge.net/doc/fitstopnm.html
118netpbm documentation 2 August 2015 Fitstopnm User Manual(0)