Glossary definition of Portable Network Graphics

Also known as: PNG

PNG (Portable Network Graphic) is an image format standard for storing graphic data. It supercedes JPEG and GIF, andimproves onfeatures of both.

PNG supports a variable colour depth of anywhere between 8 bit through to 48 bit colour (either palletized or truecolour), or 1 to 16 bit greyscale. PNG also supports full 8 bit alpha transparency, with 256 levels of opacity, which is great for making translucent gradients and a vast improvement on the either on or off transparency of GIF graphics.

Portable Network Graphics images can either be lossless or lossy, giving users as much flexibility as possible between image quality and file size. Even when lossless, the PNG format achieves a good compression ratio through an algorithm that builds on lessons learned from the way that GIF and JPEG formats have been used.

PNG supports many more features including gamma correction, layers, 2D interlacing, animation, and integrity checking. The full PNG specification can be found over at