PNG: The Definitive Guide

Chapter 1. An Introduction to PNG

PNG,[1] short for “Portable Network Graphics,” is a computer file format for storing, transmitting, and displaying images. Similar to the GIF and TIFF image formats--in fact, designed to replace them in many applications--PNG supports lossless compression, transparency information, and a range of color depths. PNG also supports more advanced features such as gamma correction and a standard color space for precise reproduction of image colors on a wide range of systems and embedded textual information for storing such things as a title, the author's name, and explicit copyright.

In this chapter, we'll consider PNG from the perspective of a user who has some familiarity with the process of creating and using computer images, but insufficient knowledge of the technical differences between various formats to be certain when to use what. I won't dwell on features that are mostly of concern to developers; where I do bring up programming issues, it is principally to explain to the user why some software may not perform as well as expected. I'll concentrate on two areas to which PNG is particularly well suited: as an intermediate editing format for repeatedly saving and restoring images without loss, and as a final display format for the World Wide Web. And I'll finish up with an in-depth look at one application that has particularly good PNG support: Macromedia's Fireworks 1.0, an image-editing program specifically designed for creating web images.