REC-png.html

PNG (Portable Network Graphics) Specification

Version 1.0

W3C Recommendation 01-October-1996

17. Appendix: Revision History

The PNG format has been frozen since the Ninth Draft of March 7, 1995, and all future changes are intended to be backwards compatible. The revisions since the Ninth Draft are simply clarifications, improvements in presentation, and additions of supporting material.

On 1 October 1996, the PNG specification was approved as a W3C (World Wide Web Consortium) Recommendation. At that time, it was awaiting publication as an Informational RFC.

Changes since the Tenth Draft of 5 May, 1995

• Clarified meaning of a suggested-palette PLTE chunk in a truecolor image that uses transparency
• Clarified exact semantics of sBIT and allowed sample depth scaling procedures
• Clarified status of spaces in tEXt chunk keywords
• Distinguished private and public extension values in type and method fields
• Added a "Creation Time" tEXt keyword
• Macintosh representation of PNG specified
• Added discussion of security issues
• Added more extensive discussion of gamma and chromaticity handling, including tutorial appendixes
• Clarified terminology, notably sample depth vs. bit depth
• Added a glossary
• Editing and reformatting