pnmtopng(1)                                           pnmtopng(1)

NAME
       pnmtopng  - convert a portable anymap into a Portable Net-
       work Graphics file

SYNOPSIS
       pnmtopng  [-verbose]  [-downscale]  [-interlace]   [-alpha
       file]
       [-transparent color] [-background color] [-gamma value]
       [-hist] [-chroma wx wy rx ry gx gy bx by] [-phys x y unit]
       [-text file] [-ztxt file] [-time [yy]yy-mm-dd hh:mm:ss]
       [-filter type] [-compression level] [-force] [pnmfile]

DESCRIPTION
       Reads a portable pixmap as  input.   Produces  a  Portable
       Network Graphics file as output.

       Color values in PNG files are either eight or sixteen bits
       wide, so pnmtopng will automatically scale colors to  have
       a  maxval  of  255 or 65535.  Grayscale files will be pro-
       duced with bit depths 1, 2, 4, 8 or 16.  An extra pnmdepth
       step is not necessary.

OPTIONS
       -verbose
              Display the format of the output file.

       -downscale
              Enables  scaling of maxvalues of more then 65535 to
              16 bit. Since this means loss of  image  data,  the
              step is not performed by default.

       -interlace
              Creates an interlaced PNG file (Adam7).

       -alpha file
              The alpha channel of pixel (or image) specifies the
              transparency of a pixel.   To  create  this  fourth
              pixel  value  a  separate  .pbm-  or  .pgm-file  is
              needed. In this file black  (0)  stands  for  fully
              transparant  and  white (1) will become opaque. The
              sizes of both pbm/pgm/ppm-files must be  the  same.
              If  the information contained in the alpha mask can
              also be represented as  a  transparency  index,  it
              will be used, since this should result in a smaller
              image file.

       -transparent color
              Allows to make one particular color fully transpar-
              ent.  The  format  to  specify  the color is either
              (when for example 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.

       -background color
              To  create  a  background  color chunck in the png-
              file, which can be used for subsequent  alpha-chan-
              nel  or  transparent-color conversions. See -trans-
              parent for format of color.

       -gamma value
              Creates an gAMA chunk. By providing the gamma-value
              of the pnm-file the software that lateron will dis-
              play the png-file will be able to do the  necessary
              gamma-corrections.  A  good  rule-of-thumb  is that
              when the file is  created  by  a  software  program
              (like  a  CAD-program or a ray-tracer) the value is
              probably 1.0. When the pnm-file  looks  good  on  a
              non-gamma  corrected PC display (which has itself a
              gamma-value of 2.2 - 2.8), a value of  0.45  should
              be given.

       -hist  Use this parameter to create a chunk that specifies
              the frequency (or histogram) of the colors  in  the
              image.

       -chroma white point X and Y, red X and Y, green X and Y,
              and blue X and Y
              To specify the white point and rgb values following
              the CIE-1931 spec.

       -phys x y unit
              When your image should not be displayed with square
              but  with  rectangular pixels this option should be
              used to create a pHYS chunk. When the unit-value is
              0  the  x and y only gives the ratio of pixel width
              and height. When it is 1 the x and  y  specify  the
              number of pixels per meter.

       -text file
              Allows to include comments in the text-chunk of the
              png-file.  The format of the text-file is  as  fol-
              lows:  when  the  first  column  does not contain a
              blank or a tab, the first word is considered to  be
              the  keyword.   For  keywords  to  contain  spaces,
              enclose them in double-quotes.
              When the first character on a line is  a  blank  or
              tab, the rest of the line is a new line of the cur-
              rent comment.  Note that the initial spaces are not
              considered to be part of the comment line.

              Here is an example:
              -------------------------------------------
              Title           PNG-file
              Author          your name
              Description     how to include a text-chunk
                              into a PNG file
              "Creation date" 3-feb-1987
              Software        pnmtopng
              -------------------------------------------

       -ztxt file
              The  same  as  -text, but now the text will be com-
              pressed.

       -time yy-mm-dd hh:mm:ss or -time yyyy-mm-dd hh:mm:ss
              This option allows you to  specify  the  (modifica-
              tion)time.  The  year  parameter  can be given as a
              two- or a four-digit value.

       -filter type
              When the types of filters must  be  restricted  you
              can  specify  here  which  filter  you want to use.
              Allowed values are: 0 (none), 1 (sub),  2  (up),  3
              (avg) and 4 (paeth).

       -compression level
              To explicitly set the compression level of zlib use
              this parameter. Select a level  between  0  for  no
              compression  (max speed) and 9 for maximum compres-
              sion.

       -force When set, -force limits the optimizations  of  pnm-
              topng.  A  png-file  similar to the pnm-input is as
              much as possible enforced. For example no  paletted
              files will be created and alpha-channel images will
              not be converted  to  images  with  a  transparency
              chunck.

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

SEE ALSO
       pngtopnm(1), gif2png(1), pnmgamma(1), pnm(5)

NOTE
       Instead of xxxtopnm|pnmtopng, a specific converter  should
       be  used,  if  available.  E.g.  gif2png (GIF 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 opti-
       mizing.

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

                          6 January 1997                        1