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)