Unlike GIFs, JPEGs have neither transparency nor animation features. A newer strand of JPEG called
Progressive JPEG gives you the interlacing option of the GIF format, however. Although not all browsers
support the interlacing feature of Progressive JPEG, they render the image regardless.
PNG
The latest entry into the Web graphics arena is the Portable Network Graphics format, or PNG. Combining
the best of both worlds, PNG has lossless compression??”meaning no pixels are lost when the file is compressed
??”like GIF, and is capable of rendering millions of colors, like JPEG. Moreover, PNG offers an interlacing
scheme that appears much more quickly than either GIF or JPEG, as well as superior transparency
support.
One valuable aspect of the PNG format enables the display of PNG pictures to appear more uniform across
various computer platforms. Generally, graphics made on a PC look brighter on a Macintosh, and Macmade
images seem darker on a PC. PNG includes gamma correction capabilities that alter the image
depending on the computer used by the viewer.
Before the 4.0 versions, the various browsers supported PNG only through plugins. After PNG was
endorsed as a new Web graphics format by the W3C, both 4.0 versions of Netscape and Microsoft browsers
added native, inline support of the new format for Windows and full PNG support is finally available in
Internet Explorer 7.
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