pngtopnm

pngtopnm(1)                 General Commands Manual                pngtopnm(1)

NAME
       pngtopnm  -  convert  a  Portable  Network  Graphics file into 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,  trans-
              parency 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 for-
              mat,  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  de-
              scribed  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.

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 conversion), etc.

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

       The program could be much faster, with a bit of code optimizing.

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

                                6 January 1997                     pngtopnm(1)