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.
This program is part of Netpbm.
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.
The program tells you what kind of PNM image it is writing.
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.
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.
This is for use in shell programs. Example:
eval 'fitstopnm -printmax $filename | \
awk {min = $1; max = $2} \
END {print "min=" min; " max=" max}'
You may need to pass the output of fitstopnm through pamflip -topbottom. See pamtofits