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Many different types of graphic file formats
exist, but three graphic file formats are generally used in web
pages—GIF, JPEG, and PNG. Currently, GIF and JPEG file formats
are the best supported and can be viewed by most browsers.
PNG files are best suited for almost any type of web graphic due
to their flexibility and small file size; however, the display
of PNG images is only partially supported in Microsoft Internet
Explorer (4.0 and later browsers) and Netscape Navigator (4.04
and later browsers). So unless you are designing for a specific
target audience using a browser that supports the PNG format,
use GIFs or JPEGs for broader appeal.
GIF (Graphic Interchange Format) files use a maximum of 256
colors, and are best for displaying noncontinuous-tone images or
those with large areas of flat colors, such as navigation bars,
buttons, icons, logos, or other images with uniform colors and
tones.
JPEG (Joint Photographic Experts Group) file format is the
superior format for photographic or continuous-tone images,
because JPEG files can contain millions of colors. As the
quality of a JPEG file increases, so does the file size and the
file download time. You can often strike a good balance between
the quality of the image and the file size by compressing a JPEG
file.
PNG (Portable Network Group) file format is a patent-free
replacement for GIFs that includes support for indexed-color,
grayscale, and true-color images, and alpha channel support for
transparency. PNG is the native file format of Macromedia
Fireworks MX. PNG files retain all the original layer, vector,
color, and effects information (such as drop shadows), and all
elements are fully editable at all times. Files must have the .png
file extension to be recognized as PNG files by Macromedia
Dreamweaver MX. |
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