pnmtopng(1)                                           pnmtopng(1)

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

       pnmtopng  [-verbose]  [-downscale]  [-interlace]   [-alpha
       [-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]

       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.

              Display the format of the output file.

              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.

              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

       -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-

       -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-

       -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

       All flags can be abbreviated to their shortest unique pre-

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

       Instead of xxxtopnm|pnmtopng, a specific converter  should
       be  used,  if  available.  E.g.  gif2png (GIF conversion),

       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-

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

                          6 January 1997                        1