pnmtopng

       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 produced 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  con-
              tained  in  the  alpha  mask can also be represented as a trans-
              parency index, it will be used, since this should  result  in  a
              smaller image file.

       -transparent color
              ppmtogif  marks  the  specified  color as transparent in the PNG
              image.

              You  specify  the  color   as   in   ppmmake(1).E.g.    red   or
              rgb:ff/00/0d.   If  the  color you specify is not present in the
              image, pnmtopnm selects instead the color in the image  that  is
              closest  to  the  one  you  specify.  Closeness is measured as a
              cartesian distance between colors in  RGB  space.   If  multiple
              colors  are  equidistant, pnmtopnm chooses one of them arbitrar-
              ily.

              However, if you prefix your color specification with "=", e.g.

              versions. See -transparent for format of color.

       -gamma value
              Creates  an gAMA chunk. By providing the gamma-value of the pnm-
              file the software that lateron will display 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  fre-
              quency (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 follows: 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 current 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 compressed.

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

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 optimizing.

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



                                6 January 1997                     pnmtopng(1)
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