png2ico(1)png2ico(1)NAMEpng2ico - convert .PNG file(s) to Windows .ICO icon resource
SYNOPSISpng2ico outfile.ico [--colors <num>] infile1.png [infile2.png ...]
DESCRIPTIONpng2ico 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
image closest to its desired resolution and will then scale it if nec‐
essary.
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.
FAVICON.ICO
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="image/x-icon">
EXAMPLES
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
BUGS
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
always 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.
AUTHOR
Matthias S. Benkmann <matthias@winterdrache.de>.
png2ico lives at http://www.winterdrache.de/freeware
SEE ALSOconvert(1), gimp(1)
1 June 2002 png2ico(1)
