Short: PNG specification (AmigaGuide format) Author: Philippe.Duchenne@ping.be (Philippe Duchenne) Uploader: Philippe Duchenne ping be (Philippe Duchenne) Type: docs/hyper Version: 1.1 Replaces: docs/hyper/PNG-guide.lha Architecture: generic PNG (Portable Network Graphic) specification supplied by the W3C (World Wide Web Consortium). Converted from HTML using GoldED and my fingers ;-) 21 Dec. 1996 (1.1): Just added a line so now the index button point to the index page. PNG is supposed to become a new standard for pictures on the Web, it also has several advantages over the GIF format. GIF features retained in PNG include: - Indexed-color images of up to 256 colors. - Streamability: files can be read and written serially, thus allowing the file format to be used as a communications protocol for on-the-fly generation and display of images. - Progressive display: a suitably prepared image file can be displayed as it is received over a communications link, yielding a low-resolution image very quickly followed by gradual improvement of detail. - Transparency: portions of the image can be marked as transparent, creating the effect of a non-rectangular image. - Ancillary information: textual comments and other data can be stored within the image file. - Complete hardware and platform independence. - Effective, 100% lossless compression. Important new features of PNG, not available in GIF, include: - Truecolor images of up to 48 bits per pixel. - Grayscale images of up to 16 bits per pixel. - Full alpha channel (general transparency masks). - Image gamma information, which supports automatic display of images with correct brightness/contrast regardless of the machines used to originate and display the image. - Reliable, straightforward detection of file corruption. - Faster initial presentation in progressive display mode. PNG is designed to be: - Simple and portable: developers should be able to implement PNG easily. - Legally unencumbered: to the best knowledge of the PNG authors, no algorithms under legal challenge are used. (Some considerable effort has been spent to verify this.) - Well compressed: both indexed-color and truecolor images are compressed as effectively as in any other widely used lossless format, and in most cases more effectively. - Interchangeable: any standard-conforming PNG decoder must read all conforming PNG files. - Flexible: the format allows for future extensions and private add-ons, without compromising interchangeability of basic PNG. - Robust: the design supports full file integrity checking as well as simple, quick detection of common transmission errors.