pngtopnm  -  convert  a  Portable  Network  Graphics file into portable


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


   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.


          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  picture  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 picture darker.

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

   -time  Prints the tIME chunk to stderr.

   All flags can be abbreviated to their shortest unique prefix.


   pnmtopng(1), ptot(1), pnmgamma(1), pnm(5)


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


   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 optimizing.


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

                            6 January 1997                     pngtopnm(1)


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