|
Graphics_for_the_web_The_Most_Common_Formats
| Graphics for the web: The Most Common Formats
One of the early problems on the net was how to display
graphics. The first browsers only displayed textual information
- the modern browser with it's images, multimedia and plugin's
did not exist. Everything was text based.
Now there are hundreds of image formats, although only a handful
are actually appropriate for the internet. And to make things
even more confusing, there are additional ways to display
pictures including Java, ActiveX, Dynamic HTML and so on
(although these tend to just display variations on the standard
web graphics formats).
And if that wasn't bad enough, email and newsgroups never
evolved a real, built-in standard for images. These two formats
are text based and have remained so in spite of the changes in
browsers and technology. Special encoding technology has been
created to allow attachments to be sent with messages. Most of
the modern email clients detect this and perform the conversion
automatically.
For the web, the dominant formats are GIF and JPEG. BMP (bit
mask images) are occasionally used, and the up-and-coming PNG
format seems poised to threaten GIF in a few years. The GIF
format is perhaps the oldest and most powerful of the formats
(except for the limitation of 256 colors), since it supports
animation, interlacing and transparency. The other dominant
format, JPG, tends to create smaller, albeit fuzzier images.
The three major web formats for graphics are described briefly
below.
GIF (Graphics Interchange Format) - This is probably the most
widely used format on the internet. It was created by CompuServe
in 1987 to display images on their service. Some of the great
features of this graphics format include:
- Excellent compression - images created in the GIF format can
be optimized to very small sizes.
- Interlacing - Allows images to "fade" in slowly. This is very
useful for large images.
- Transparency - The ability to make a color be transparent,
allowing the background of the web page to show through.
- Animation - You can tie together multiple images to create
animation.
The problems of GIF are:
- GIF uses a proprietary encoding/decoding scheme called LZW
(Lempel Zev Welch). This scheme is patented by Unisys, who has
been sending out letters demanding compensation from some
companies who have created commercial image applications.
- GIF images can only include 256 colors.
JPEG (Joint Photographic Experts Group) - Another very common
format on the internet. JPEG (also known as JPG) images use a
lossy compression scheme. This means that as you optimize your
image bits are removed. When the image is decompressed, the bits
are interpolated. This means that as you use greater and greater
compression, your image tends to get fuzzier and fuzzier.
This format is best for images with gradients, such as paintings
and photos. Images with sharp definition, such as clipart and
text, should be saved as GIF or PNG.
JPEG images can often be compressed to smaller sizes than the
exact same image in GIF format, although some definition may be
lost. Depending upon the image, this may or may not be important.
The main reason why JPEG images would be used instead of GIF is
that JPEG's support more than 256 colors.
PNG (Portable Network Graphics) - PNG is a new, up-and-coming
format. PNG has all of the features of GIF except for animation,
and PNG has the advantage of allowing for more than 256 colors.
In addition, the compression algorithm of PNG is public domain
and non-lossy (bits of the image are not lost), which makes it
superior to both GIF and JPG.
All of the newer browsers support PNG format, including Netscape
and Internet Explorer. You should still use this format with
caution, as older browsers do not support it at all. Thus, if
you use the format you are more-or-less locking out those who
have not upgraded their browsers.
About the author:
Richard Lowe Jr. is the webmaster of Internet Tips And Secrets.
This website includes over 1,000 free articles to improve your
internet profits, enjoyment and knowledge. Web Site Address:
http://www.internet-tips.net Weekly newsletter:
http://www.internet-tips.net/joinlist.htm Daily Tips:
mailto:internet-tips@GetResponse.com
|
|
| |
| |
