pnmtopng(1)						      General Commands Manual						       pnmtopng(1)

NAME
       pnmtopng - convert a portable anymap into a Portable Network 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 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 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
	      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 arbitrarily.

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

	      -transparent =red

	      Only the exact color you specify will be transparent.  If that color does not appear in the image, there will  be  no  transparency.
	      pnmtopng issues an information message when this is the case.

       -background color
	      To  create  a  background  color chunck in the png-file, which can be used for subsequent alpha-channel or transparent-color conver-
	      sions. 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-pro-
	      gram 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 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  dou-
	      ble-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 ini-
	      tial 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.

       -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 compression.

       -force When set, -force limits the optimizations of pnmtopng. 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 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)