portable network graphics (file format) (PNG)
The PNG (Portable Network Graphics) file format was developed by the World Wide Web Consortium (W3C) and published by the Internet Engineering Task Force( IETF) in RFC 2083 in 1997. It was standardized by ISO/ IEC.
The royalty-free format is similar to the Graphics Interchange Formats( GIF) and is considered its successor. In contrast to the GIF file format, which has a color depth of 8 bits, PNG works with a color depth of 8 or 16 bits per channel and thus achieves the color depth of True Color in color representation. Portable Network Graphics (PNG) works with the RGB color model, with indexed colors or grayscale.
The PNG file format combines the advantages of Graphics Interchange Format (GIF) and JPEG, it has lossless compression and is supported by all modern web browsers such as Navigator (4.0) and Internet Explorer (4.0), as well as many graphics programs. The files are larger than those of JPEG due to the high resolution and the lossless compression according to the LZ method( Lempel, Ziv, LZ77). When loading a graphic, it first appears in rough structure before it is resolved in detail.
PNG has an alpha channel for transparent representations and can store keywords and text in addition to the graphic. Furthermore, PNG has error control with integrity checking. Whenextended as Animated PNG( APNG), the APNG form supports animated images. It recognizes the Extensible Metadata Platform(XMP) metadata format, but not Exchangeable Image File( EXIF) and International Press Telecommunications Council( IPTC).
The file extensions are *.png and *.pngf.