Introduction

Portable Network Graphics (PNG), is a raster graphics file format that supports lossless data compression. PNG was created as an improved, non-patented replacement for Graphics Interchange Format (GIF), and is the most used lossless image compression format on the Internet.

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

PNG files nearly always use file extension PNG or png and are assigned MIME media type image/png. PNG was approved for this use by the Internet Engineering Steering Group on 14 October 1996, and was published as an ISO/IEC standard in 2004.

Usage

References

1. http://en.wikipedia.org/wiki/Portable_Network_Graphics
2. http://www.libpng.org
3. http://www.libpng.org/pub/png/
4. http://www.libpng.org/pub/png/libpng.html