pngtopnm(1)                                                   General Commands Manual                                                  pngtopnm(1)

NAME

       pngtopnm - convert a Portable Network Graphics file into portable anymap

SYNOPSIS

       pngtopnm [-verbose] [-alpha | -mix] [-background color]
       [-gamma value] [-text file] [-time] [pngfile]

DESCRIPTION

       Reads a Portable Network Graphics as input.  Produces a portable anymap as output.  The type of the output file depends on the input file -
       if it's black & white, a pbm file is written, else if it's grayscale a pgm file, else a ppm file.

OPTIONS

       -verbose
              Display the format of the input file and the type of the output file. If the chunks are part of  the  png-file,  the  alpha,  trans-
              parency and gamma-values will be indicated.

       -alpha Output  the  alpha channel or transparency mask of the image. The result is either a pbm file or pgm file, depending on whether dif-
              ferent levels of transparency appear.

       -mix   Compose the image with the transparency or alpha mask against a the background. When a background chunk is available that  color  is
              taken, else black will do.

       -background color
              If  no  background  color chunck is present in the png-file, or when another color is required this parameter can be used to set the
              background color of images. This is especially useful for alpha-channel images or those with transparency  chunks.  The  format,  to
              specify the color in, is either (in the case of 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.

       -gamma value
              Converts the image to a new display-gamma value. When a gAMA chunk is present in the png-file, the image-gamma value will  be  used.
              When  not, the image-gamma is considered to be 1.0. Based on the image-gamma and the display-gamma given with this option the colors
              written to the pnm-file will be adjusted.
              Because the gamma's of uncompensated monitors are around 2.6, which results in an image-gamma of 0.45, some typical situations  are:
              when  the  image-gamma is 0.45 (use -verbose to check) and the picture is too light, your system is gamma-corrected, so convert with
              "-gamma 1.0".  When no gAMA chunk is present or the image-gamma is 1.0, use 2.2 to make the picture lighter and  0.45  to  make  the
              picture darker.

       -text file
              Writes the tEXt and zTXt chunks to a file, in a format as described in the pnmtopng man-page.  These chunks contain text comments or
              annotations.

       -time  Prints the tIME chunk to stderr.

       All flags can be abbreviated to their shortest unique prefix.

SEE ALSO

       pnmtopng(1), ptot(1), pnmgamma(1), pnm(5)

NOTE

       Instead of pngtopnm|pnmtoxxx, a specific converter should be used, if available. E.g.  ptot (PNG to TIFF 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                                                       pngtopnm(1)