Info Tech Guide

PNG Stands for "Portable Network Graphic." This format was designed as an alternative to the Graphics Interchange Format (GIF). Like GIFs, PNG files are lossless, meaning they don't lose any detail when they are compressed. They support up to 48-bit color or 16-bit grayscale and typically compress about 5% to 25% better than GIF files. However, they do not support animations like GIFs do. A format similar to PNG, called MNG, is currently under development, and will support animations.

PNG was approved as a standard by the World Wide Web consortium to replace GIF because GIF uses a patented data compression algorithm called LZW. In contrast, PNG is completely patent- and license-free. The most recent versions of Netscape Navigator and Microsoft Internet Explorer now support PNG.

PNG supports palette-based images (with palettes of 24-bit RGB or 32-bit RGBA colors), greyscale images (with or without alpha channel), and RGB[A] images (with or without alpha channel). PNG was designed for transferring images on the Internet, not for print graphics, and therefore does not support non-RGB color spaces such as CMYK.

Like a GIF, a PNG file is compressed in lossless fashion (meaning all image information is restored when the file is decompressed during viewing). A PNG file is not intended to replace the Joint Photographic Experts Group (JPEG), which is "lossy" but lets the creator make a trade-off between file size and image quality when the image is compressed. Typically, an image in a PNG file can be 10 to 30% more compressed than in a GIF format.