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Last updated Oct 17, 2003.
PNG, which stands for Portable Network Graphics, uses lossless compression, which means that the image loses no quality. Unlike GIF, PNG is patent-free (not owned). PNG offers palette-based support, grayscale support up to 16-bit, truecolor support, alpha channel for transparency, and direct support for gamma correction and color correction.
Gamma correction allows an image that displays properly on different platforms without losing brightness or contrast. View an image on a Macintosh and a PC, and you see a difference. Macs display images darker and PCs display images lighter. An image created on either platform won't look right on the other platform or even on its own. Without going into highly technical details, PNG's storing of gamma information enables the system to use the correct gamma value, if it has one. Sounds great, but there's a catch: Not all systems know their own gamma values.
If PNG is so great in that it offers alpha channel (RGBa) where GIF only offers RGB, why isn't PNG more widely in use? Early browser versions didn't support PNG and companies behind Web sites didn't want to desert those using such browsers. Like BETA videotapes, it offers excellent quality, but hasn't gained the support it needs to succeed. However, that can change, and it's still possible for PNG to gain respect, but beware: It is also possible that it may never become widely used.