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,  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.

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 instead 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)