XnView Software

Adobe (Embedding XMP Metadata in Application Files — [url=http://www.google.com/search?q=cache:xml.coverpages.org/XMP-Embedding.pdf#8]14/Sep/2001 Draft[/url]) wrote:An XML packet can be embedded in a PNG graphic file by adding a chunk of type “tXMP”.
The data of the chunk should be a UTF-8 serialized XML packet.

There should be no more than one ‘tXMP’ chunk present in each PNG file. Encoders are encouraged to place the chunk at the beginning of the file, but this is not a requirement.

Adobe (Embedding XMP Metadata in Application Files — [url=http://www.google.com/search?q=cache:partners.adobe.com/public/developer/en/xmp/sdk/XMPEmbedding.pdf#8]06/Jun/2002 Draft[/url]) wrote:An XML packet can be embedded in a PNG graphic file by adding a chunk of type “iTXt”.
This chunk is semantically equivalent to the tEXt and zTXt chunks, but the textual data is in the UTF-8 encoding of the Unicode character set, instead of Latin-1.

The Chunk Data portion is the XML packet. The packet must be marked as read-only.

NOTE: XMP software that is not aware of the file format must not be allowed to change the content of the XML packet because of the CRC checksum following the chunk data. This is why the packet must be marked as read-only.

There should be no more than one iTXt chunk present in each PNG file. Encoders are encouraged to place the chunk at the beginning of the file, but this is not a requirement.

• Adobe Extensible Metadata Platform (XMP) — Adding intelligence to media
  • XMP Specification (January 2004)
    • Page 76: JPEG 2000
    • Page 79: PNG
  • XMP Specification (June 2005)
    • Page 94: JPEG 2000
    • Page 97: PNG
• ExifTool
  • ExifTool Tag Names
    • EXIF
    • XMP
    • Jpeg2000
    • PNG