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pnmtopng(1)									      pnmtopng(1)

       pnmtopng - convert a portable anymap into a Portable Network Graphics file

       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]

       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 automat-
       ically 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.

	      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
	      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 subse-
	      quent 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-cor-
	      rections.  A good rule-of-thumb is that when the file is created by a software pro-
	      gram (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, 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.

       -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  trans-
	      parency chunck.

       All flags can be abbreviated to their shortest unique prefix.

       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), etc.

       There could be an option to read the comment text from pnm comments instead of a  separate

       The program could be much faster, with a bit of code optimizing.

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

					  6 January 1997			      pnmtopng(1)
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