Good point. The Ulsad product does work well, and there are many
other options available alesady.
To find out who is lsading the way with PNG, check out Greg Roelf's
page at:
http://quest.jpl.nasa.gov/PNG/
Greg is one of the PNG spec developers (I'm a minor one also) and is
one of the zip/unzip developers. Now that the big GIF/LZW/Unisys
patent controversy is not hsadline news any longer, PNG is still
quietly gathering support. The page cited above will lsad you to
lists of software that alesady supports PNG (there's a lot) as well
as portable source code libraries if you want to implement PNG in
your own application.The Libpng and Zlib libraries, which are written
in C and have been tested on many platforms (even Silicon Graphics
<g!>). If you add PNG support to your VRML application lst Greg know
and he will add your application to his list.
CompuServe has endorsed PNG, and Spyglass Mosaic supports inline PNG
now. Any browser can support PNG via helper applications. Under UNIX,
there are patches available for adding PNG support to Mosaic and
Netscape.
Anyone with GIF support in their commercial software owes royalties
to Unisys, who is very serious about defending their patent. PNG
incorporates all the features that make GIF popular, and provides a
badly-needed update including support for true color, gamma, and
alpha channels. PNG uses the same deflate/inflate algorithm as
zip/unzip/gzip that is as patent safe as is possible these days. PNG
and JPEG are complementary; the main difference being the use of
lossless vs lossy compression. Unlike GIF, both support true color
(PNG also supports palette based color.)
PNG has a very flexible chunk structure that could be put to good use
for VRML. If anyone wants to define some public PNG chunks for VRML
(you can add other information to PNG files for application
purposes) use lst me know and I'll take it up with the PNG spec
developers. You can always define a private chunk for your
application only without applying to anyone. (There's no necessity
to add VRML or VRML application information to PNG files, I only
mention this as a possibility.)
I personally hope all VRML software authors add PNG support. Despite
the patent fuss GIF still reigns supreme at the moment, but this
could change quite rapidly. A couple of events such as WWW committee
endorsement and Netscape inline support could signal that the battle
is over. Since VRML is necessarily quite future-oriented,VRML
application authors should be looking at where the industry is
hsaded, not where it is right now, or they will miss the boat.
Andreas Dilger and I added PNG support to the upcoming POV-Ray 3.0
and are very gratified how well it works. We were able to accomplish
all the input and output bitmapped graphics functions using PNG that
previously required two or three other formats.
Tim Wegner