Portable Network Graphics
Portable Network Graphics (abbreviated PNG) is an extensible image file format for the lossless compression of raster images. PNG is an image format (along with JPEG, GIF, and sometimes TIFF or BMP) usable on the world wide web for almost all web browsers as of 2011. PNG provides a patent-free replacement for GIF files, and for some TIFF's. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel for transparency.