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PNG (Portable Network Graphics) Specification Version 1.0 (RFC2083)

IP.com Disclosure Number: IPCOM000002635D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2000-Sep-13

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

T. Boutell: AUTHOR

Abstract

This document describes PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 1% of the total text.

Network Working Group T. Boutell, et. al.

Request for Comments: 2083 Boutell.Com, Inc.

Category: Informational March 1997

PNG (Portable Network Graphics) Specification

Version 1.0

Status of this Memo

This memo provides information for the Internet community. This memo

does not specify an Internet standard of any kind. Distribution of

this memo is unlimited.

IESG Note:

The IESG takes no position on the validity of any Intellectual

Property Rights statements contained in this document.

Abstract

This document describes PNG (Portable Network Graphics), an

extensible file format for the lossless, portable, well-compressed

storage of raster images. PNG provides a patent-free replacement for

GIF and can also replace many common uses of TIFF. Indexed-color,

grayscale, and truecolor images are supported, plus an optional alpha

channel. Sample depths range from 1 to 16 bits.

PNG is designed to work well in online viewing applications, such as

the World Wide Web, so it is fully streamable with a progressive

display option. PNG is robust, providing both full file integrity

checking and simple detection of common transmission errors. Also,

PNG can store gamma and chromaticity data for improved color matching

on heterogeneous platforms.

This specification defines the Internet Media Type image/png.

Table of Contents

1. Introduction .................................................. 4

2. Data Representation ........................................... 5

2.1. Integers and byte order .................................. 5

2.2. Color values ............................................. 6

2.3. Image layout ............................................. 6

2.4. Alpha channel ............................................ 7

2.5. Filtering ................................................ 8

2.6. Interlaced data order .................................... 8

2.7. Gamma correction ......................................... 10

2.8. Text strings ............................................. 10

3. File Structure ................................................ 11

3.1. PNG file signature ....................................... 11

3.2. Chunk layout ............................................. 11

3.3. Chunk naming conventions ................................. 12

3.4. CRC algorithm ............................................ 15

4. Chunk Specifications .......................................... 15

4.1....