pngtopnm(1)

NAME
       pngtopnm - convert a Portable Network Graphics file into a
       portable anymap

SYNOPSIS
       pngtopnm [-verbose] [-alpha | -mix] [-background color]
       [-gamma value] [-text file] [-time] [pngfile]

DESCRIPTION
       Reads a Portable Network Graphics as  input.   Produces  a
       portable  anymap  as  output.  The type of the output file
       depends on the input file - if it's black & white,  a  pbm
       file is written, else if it's grayscale a pgm file, else a
       ppm file.

OPTIONS
       -verbose
              Display the format of the input file and  the  type
              of  the  output file. If the chunks are part of the
              png-file, the alpha, transparency and  gamma-values
              will be indicated.

       -alpha Output  the  alpha  channel or transparency mask of
              the image. The result is either a pbm file  or  pgm
              file,  depending  on  whether  different  levels of
              transparency appear.

       -mix   Compose the image with the  transparency  or  alpha
              mask  against  a  the background. When a background
              chunk is available that color is taken, else  black
              will do.

       -background color
              If  no  background  color  chunck is present in the
              png-file, or when another color  is  required  this
              parameter  can  be used to set the background color
              of images. This is  especially  useful  for  alpha-
              channel  images  or those with transparency chunks.
              The format, to specify the color in, is either  (in
              the case of orange) "1.0,0.5,0.0", where the values
              are floats between zero and one, or with the syntax
              "#RGB", "#RRGGBB" or "#RRRRGGGGBBBB" where R, G and
              B are hexa-decimal numbers.

       -gamma value
              Converts the image to a  new  display-gamma  value.
              When  a  gAMA chunk is present in the png-file, the
              image-gamma value  will  be  used.  When  not,  the
              image-gamma  is  considered to be 1.0. Based on the
              image-gamma and the display-gamma given  with  this
              option  the  colors written to the pnm-file will be
              adjusted.
              Because the gamma's of uncompensated  monitors  are
              around  2.6,  which  results  in  an image-gamma of
              0.45, some typical situations are: when the  image-
              gamma  is 0.45 (use -verbose to check) and the pic-
              ture is too light, your system is  gamma-corrected,
              so  convert  with "-gamma 1.0".  When no gAMA chunk
              is present or the image-gamma is 1.0,  use  2.2  to
              make  the picture lighter and 0.45 to make the pic-
              ture darker.

       -text file
              Writes the tEXt and zTXt chunks to  a  file,  in  a
              format as described in the pnmtopng man-page.

       -time  Prints the tIME chunk to stderr.

       All flags can be abbreviated to their shortest unique pre-
       fix.

SEE ALSO
       pnmtopng(1) ptot(1) pnmgamma(1) pnm(5) 

NOTE
       Instead of pngtopnm|pnmtoxxx, a specific converter  should
       be  used,  if  available.  E.g.  ptot (PNG to TIFF conver-
       sion), etc.

BUGS
       There could be an option to read the comment text from pnm
       comments instead of a separate file.

       The program could be much faster, with a bit of code opti-
       mizing.

AUTHORS
       Copyright (C) 1995-1997 by Alexander Lehmann
                               and Willem van Schaik.