LIS 525 - Multimedia
Graphics Formats
Only a few graphics formats are generally supported
by Web browsers.
JPEG and GIF are generally supported.
The newer PNG format is supported by newer browsers.
Web graphics formats are generally bitmapped (raster),
which makes them not particularly efficient for simple shapes,
though compression can reduce file size considerably.
GIF (pronounced "jiff")
(Graphics Interchange Format) supports up to 256 colors
and allows one color to be defined as the transparent
color.
GIF includes data compression
but is not lossy
(except for the limitation on the number of colors).
Because GIF generally used a patented data compression algorithm
(called LZW),
there was a move to replace it with PNG
(though the patent has now either expired
or is about to in most places).
According to Security Space (October, 2007),
about 62% of Web sites use GIF.
JPEG (Joint Photographic Experts Group)
(pronounced "jay-peg")
is a lossy compressed format for color images,
which can reduce file sizes to about 5%
of normal (.bmp) size
(though a more normal reduction would be to about 35%).
According to Security Space (October, 2007),
about 55% of Web sites use JPEG.
PNG (Portable Network Graphics)
(pronounced "ping")
is a new format, similar to GIF,
approved as a standard by the World Wide Web consortium.
PNG is completely patent- and license-free
and most features are supported by recent versions
of popular browsers.
A bug in the way Internet Explorer
and Nescape for Solaris handle PNG files,
however,
represents a potential security threat at the browser end.
Many tools still do not produce PNG files;
but some newer software does,
including Corel Photo House,
Microsoft PowerPoint, Corel Presentations, GIMP,
and some versions of Microsoft Paint.
According to Security Space (October, 2007),
about 11% of Web sites use PNG.
Audio Formats
WAV (Waveform) was developed for Microsoft Windows.
It is the only form supported by Sound Recorder.
MIDI (Musical Instrument Digital Interface)
is a format for electronic music.
It can be produced by computers, electronic keyboards, and
synthesizers.
Inexpensive music editing software
(not currently available on the FIMS LAN)
may be used to produce MIDI files.
Only a few programs are capable of converting MIDI
to other sound formats.
AU (Sun Audio) was originally designed for Sun UNIX.
AIFF (Audio Interchange Format)
was originally developed by Apple
for music and high quality sound.
Sounds may also be encoded in various MPEG formats
(.mpeg, .mpg, etc.).
WMA (Windows Media Audio)
is a Microsoft format similar to MP3 (MPEG audio layer 3)
but capable of higher compression.
An HTML page can use the embed tag
to cause an audio file to be played
while the page is being viewed;
for example,
<embed SRC="drink.wma" height="100"
width="140" autostart="true">
If plug-ins are disabled
or a suitable plug-in has not been installed,
the following embedded sound control will display as a default graphic,
except in Opera
which will just leave a blank space.
In Opera, even with plug-ins enabled,
the control is displayed,
but the sound does not play,
even when the "Play" button is clicked.