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png2ico(1)		    General Commands Manual		    png2ico(1)

       png2ico - convert .PNG file(s) to Windows .ICO icon resource

       png2ico outfile.ico [--colors <num>] infile1.png	[infile2.png ...]

       png2ico	takes  the input files and stores them in the output file as a
       Windows icon resource. Usually the input	files would all	represent  the
       same  image  in	different  resolutions	(common	resolutions are	16x16,
       32x32 and 64x64). A program reading the icon resource will pick the im-
       age  closest to its desired resolution and will then scale it if	neces-

       Using the parameter --colors you	can specify the	number	of  colors  to
       use  for	 the images that follow	--colors on the	command	line.  Allowed
       values are 2, 16	and 256. If omitted, 256 colors	will be	used. --colors
       can  be specified multiple times	to store images	with different numbers
       of colors in the	same icon file.	If the source image has	more than  the
       specified number	of colors, color reduction will	be performed.

       Most graphical browsers today support the favicon.ico file. When	a user
       bookmarks a web page, the browser will automatically check if it	 finds
       a  favicon.ico  file  on	the web	server and display it in the bookmarks
       menu.  Depending	on the browser and configuration the  favicon.ico  may
       also appear in other places.

       To  create a favicon.ico	simply create a	16x16 .PNG file	and convert it
       to an icon resource with	png2ico. You may of course add other  alterna-
       tive resolutions	but most browsers only use a 16x16 image. Keep in mind
       that for	a user with a slow modem a favicon.ico may increase  the  page
       loading	time  by a few seconds if it is	too large, so don't overdo it.
       Adding a	32x32 alternative should be enough to make sure	the image will
       look  good  even	 in  contexts  with larger icons. Adding even more and
       larger alternatives is unnecessary bloat.  Try to keep  the  number  of
       colors below 16 and create a 16-color icon using	the --colors 16	switch
       of png2ico (or even create a b/w	icon using  the	 --colors  2  switch).
       This will result	in a smaller file that loads faster.

       Don't  forget  that the favicon.ico may be composed against backgrounds
       of different colors so you should use transparency rather than a	 solid
       background if you want to avoid that your icon appears inside a box.

       To add your new favicon.ico to a	web page put it	on the server into the
       same directory as the web page. That is the 1st place  a	 browser  will
       look.  If it doesn't find an icon there,	it checks the top-level	direc-
       tory of the web server, so by putting it	there you can have  a  default
       favicon	for  all  the  pages in	your domain.  Depending	on browser and
       configuration, the favicon.ico is not always rendered, even if it is in
       one of the above	locations, unless the web page explicitly declares its
       presence. To declare that your web page has an icon, you	add  the  fol-
       lowing 2	lines into the <head> section of your page:

	      <link rel="icon" href="favicon.ico" type="image/x-icon">

	      <link	rel="shortcut icon"    href="favicon.ico"    type="im-

       To create a favicon.ico from 2 logo files (the 1st in 16x16  resolution
       and the 2nd in 32x32 resolution)	you could use the following command:

	      png2ico favicon.ico logo16x16.png	logo32x32.png

       The color reduction algorithm used by png2ico is	very slow. If you have
       an input	file with several thousand colors (very	unlikely), it may take
       several	seconds	 to create the icon. If	possible, reduce the number of
       colors in your .PNG files before	passing	them to	png2ico.

       The handling of the transparency	mask is	very inconsistent in programs.
       The  same  program will sometimes interpret it differently depending on
       context.	 png2ico takes precautions to make sure	that the icon will al-
       ways  look the same. For	doing this, png2ico uses one palette entry for
       black (0,0,0) and one palette entry for white  (255,255,255),  even  if
       the  icon  does not have	a single black or white	pixel. This means that
       2-color icons will always be black and white.  In  16/256-color	icons,
       only 14/254 colors can be chosen	freely.

       Matthias	S. Benkmann <>.

       png2ico lives at

       convert(1), gimp(1)

				  1 June 2002			    png2ico(1)


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