     pnmtopng(1)                                                     pnmtopng(1)
                                   6 January 1997

     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
               Allows to make one particular color fully transparent. 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

                                        - 1 -       Formatted:  October 17, 2001

     pnmtopng(1)                                                     pnmtopng(1)
                                   6 January 1997

               used for subsequent alpha-channel or transparent-color
               conversions. 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 frequency
               (or histogram) of the colors in the image.

          -chroma white point 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.

                                        - 2 -       Formatted:  October 17, 2001

     pnmtopng(1)                                                     pnmtopng(1)
                                   6 January 1997

          -time yy-mm-dd hh:mm:ss or -time yyyy-mm-dd
               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.

                                        - 3 -       Formatted:  October 17, 2001