PNG (Portable Network Graphic)

• developed in 1995 as alternative to GIF (because of Unisys patent on LZW compression)
• 8-bit, 16-bit grayscale, and up to 48-bit RGB support
• lossless compression, better compression than LZW
• an alpha channel with 8-bit or 16-bit transparency information, i.e. up to 65,000 shades of transparency, compared to one (one colour selected as having transparency 'on') in GIF
• gamma correction for platform independent display

Despite this impressive range of features, PNG is not widely used. The problem is browser support, which was introduced with version 4.04 of Netscape and 4.0b1 of Internet Explorer (for Windows, not till version 5 for Mac), though alpha channel transparency and gamma correction were not then supported.

PNG is best used as a replacement format for those images previously suited to GIF.

PNG should not be used as a substitute for JPEG, as it generally results in larger file sizes.