PNG: The Definitive Guide

Chapter 7. History of the Portable Network Graphics Format

Internet GIF tax,

January '95.

PNG to the rescue!

--Glenn Randers-Pehrson [47]

The Portable Network Graphics image format, or PNG for short, is the first general-purpose image format to achieve wide, cross-platform acceptance[48] since JPEG/JFIF arrived in the early 1990s. Almost every major feature in PNG exists in other general-purpose formats--specifically, GIF, JPEG, and TIFF--yet in January 1995, a group of strangers felt compelled to band together and design another image format from scratch. To understand why, it is necessary to delve even further into history.

In 1977 and 1978, Israeli researchers Jacob Ziv and Abraham Lempel published a pair of papers on a new class of lossless data-compression algorithms in the journal IEEE Transactions on Information Theory. These algorithms, now collectively referred to as “LZ77” and “LZ78,” formed the basis for an entire industry of software, hardware, and subsequent research papers. One of the follow-up papers was by Terry Welch and was published in the June 1984 issue of IEEE Computer. Entitled “A Technique for High-Performance Data Compression,” it described his research at Sperry into a fast, efficient implementation of LZ78 called LZW.

By 1987, when CompuServe's Bob Berry was busy designing the GIF image format, LZW was well established in the Unix world in the form of the compress command, and in the PC world in the form of SEA's ARC. As a fast algorithm with good compression ...