A guide to PNG optimization1. Background 1.1 The PNG file format The Portable Network Graphics (PNG) is a format for storing compressed raster graphics. The compression engine is based on the Deflate method [RFC1951], designed by PKWare and originally used in PKZIP. The PNG format is defined by the PNG Specification. This specification was developed by an ad-hoc group named the PNG Development Group, and it is both an Inter
