There are really only two types of graphics file formats in use on
the web today:
- Graphic Interchange Format or .GIF. This format was originally
promoted by CompuServe. It uses compression to reduce file size, supports
256 colors, supports transparency and interlacing, and is also used for
some kinds of GIF graphic animation. The GIF
format is probably the most "preferred" or commonly supported
by web browsers, but this is changing rapidly. Most graphics editing programs
can read and write the GIF format.
- Joint Photographic Experts Group (JPEG) or .JPG. This format
uses "lossy" compression, supports 16.7 million colors, and has
reasonably small file sizes. It does not yet support transparency, although
the JPEG spec does support progressive loading (sort of like interlacing).
JPEG FAQ
Compare the same image in these two formats.
Note: JPEG's lossy compression scheme causes a loss of image quality
every time you save the file, so this is not the format to use until after
you've finished editing the image!
- Portable Network Graphics
(PNG). ("pronounced ping") This format is the follow-on to
the GIF format. It's not in common use yet, but should result in a format
with the best of GIF and JPEG formats, but uses a lossless compression
scheme.
If you want maximum color accuracy and a small file size, but don't
need transparency or interlacing, then use the JPEG format.
If you want maximum web browser compatibility, transparency, and interlacing,
but don't need maximum colors, or small file size, then use the GIF format.
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