A PNG file contains a single image in an extensible structure of “chunks”, encoding the basic pixels and other information such as textual comments and integrity checks documented in RFC 2083. 256 colors were becoming common. PNG mac os x combine jpegs into pdf be a single-image format.
MNG achieved moderate application support, but not enough among mainstream web browsers and no usage among web site designers or publishers. 1 October 1996: Version 1. Recommendation on 1 October 1996. 31 December 1998: Version 1. 11 August 1999: Version 1.
2, adding one extra chunk, was released. This version of PNG differs only slightly from version 1. 2 and adds no new chunks. The original PNG specification was authored by an ad-hoc group of computer graphics experts and enthusiasts. Discussions and decisions about the format were conducted by email. DOS-Unix line ending conversion of the data.
The case of the first letter indicates whether the chunk is critical or not. Critical chunks contain information that is necessary to read the file. If a decoder encounters a critical chunk it does not recognize, it must abort reading the file or supply the user with an appropriate warning. Uppercase is public and lowercase is private.