| Basic Info | |
|---|---|
| Media Type | image |
| subtype | png |
| Registered? | Yes |
| See also | Randers-Pehrson |
| Extensions | PNG |
Tags: common
File Formats: (none)
From [email protected] Sat Jul 27 04:43:17 1996 Date: Sat, 27 Jul 96 8:43:17 EDT From: Glenn Randers-Pehrson ARL-WMRD-TED-TIB <[email protected]> To: [email protected] Cc: [email protected] Subject: Registration of new Media Type image/png Content-Length: 2047 Status: RO X-Lines: 50 To: [email protected] Subject: Registration of new Media Type image/png Media Type name: image Media subtype name: png Required parameters: None Optional parameters: None Encoding considerations: base64 generally preferred Security considerations: A PNG document is composed of a collection of explicitly typed "chunks". For each of the chunk types defined in the PNG specification (except for "gIFx"), the only effect associated with those chunks is to cause an image to be rendered on the recipient's display or printer. The gIFx chunk type is used to encapsulate Application Extension data, and some use of that data might present security risks, though no risks are known. Likewise, the security risks associated with future chunk types cannot be evaluated, particularly unregistered chunks. However, it is the intention of the PNG group to disallow chunks containing "executable" data to become registered chunks. The text chunks, tEXt and zTXt, contain data that can be displayed in the form of comments, etc. Some operating systems or terminals might allow the display of textual data with embedded control characters to perform operations such as re-mapping of keys, creation of files, etc. For this reason, the specification recommends that the text chunks be filtered for control characters before direct display. The PNG format is specifically designed to facilitate early detection of file transmission errors, and makes use of cyclical redundancy checks to ensure the integrity of the data contained in its chunks. Published specification: Internet-Draft draft-boutell-png-spec-04.txt, "Png (Portable Network Graphics) Specification Version 1.0" which is an "rfc-to-be." The IESG has concurred in publication of the spec as an Informational RFC; see item 11 of the IESG minutes for their meeting of 7-11-96. Person & email address to contact for further information: Glenn Randers-Pehrson, [email protected] or [email protected] Thomas Boutell, [email protected]