PNG format.
PNG stands for "Portable Network Graphic" and it is a more recent image format,
which is not yet in wide use on the Net. It is a lossless compression algorithym (same as GIF) which
in which files can be saved at a variety of bit depths, and is
purported to have 10-30% better compression than GIF. For highest quality images, the fact that
it is a lossless algorithm means that it could offer superior quality to JPEG. Promised benefits
of the PNG format are:
- Alpha channels which will allow for multiple levels of opacity for improved "transparency" in images.
- Self-adjusting gamma levels which should allow the image to look good on a variety of platforms.
- Up to 48 bit color.
- Non-patented loss-less compression.
While the format sounds very cool, support has been slow in coming from the major browsers. This has improved recently
and now you can use the regular IMG tag to inline PNG files.
Limited support for PNG is built into IE 4 and later, and Navigator 4.5. In the most recent versions of these browsers you
can display PNG files using the simple IMG tag. The main limitations with PNG now is that not all of the myriad features of the file
format are supported by both of the most popular browsers. For example, support for the alpha channels functionality of
PNG is spotty even up through IE 5.5.
Older versions of these browsers required plugins to show PNG files. There are many PNG plugins listed on the sites below, but a very common
one that has some support of PNG is the QuickTime 2.0 plugin. Use of plugins for PNG is awkward because Netscape does not support
the standard OBJECT tag, instead uses the EMBED tag. Because of this, some sites resort to redundant formatting to try and display PNG files in a wide variety of
browsers. For example:
<![CDATA[
<OBJECT WIDTH="256" HEIGHT="192" TYPE="image/png" DATA="img_png/pnglogo-blk-sml1.png">
<IMG WIDTH="256" HEIGHT="192" SRC="img_png/pnglogo-blk-sml1.gif" ALT="[PNG: 256x192 colored-balls logo]">
</OBJECT>
]]>
(So for Explorer, older version will use the OBJECT tag if they have a relevant plug-in. For Navigator, new versions will use the IMG tag and older versions require the non-standard EMBED tag which will load a plugin to view the PNG file. That code was copied from http://www.cdrom.com/pub/png/.)
To make PNG files, Fireworks is your best bet in terms of functionality. Photoshop can read and save PNG files, but it's compression is not as good and not all features are supported.
Documentation
PNG resouce information
Ping Live plugin from Siegel and Gale
Building Web Sites - ITP Fall 2000 - Mike Cosaboom, Instructor
mc39@acf2.nyu.edu