File Formats that support XMP

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JohnFredC
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File Formats that support XMP

Post by JohnFredC » Sun Apr 16, 2006 1:46 pm

Which graphic file formats support XMP/EXIF? Currently I am aware of TIFF and JPG. Are there any others? I prefer to save my images in PNG format, which apparently will never support either.

What about JPEG2000? If JPEG2000 supported XMP, I might switch to it, using lossless compression. But would there be compatibility issues between softwares using this approach?
John

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XnTriq
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Post by XnTriq » Sun Apr 16, 2006 7:15 pm

According to Adobe's XMP Developer Knowledgebase — and to my own surprise — PNG as well as JPEG 2000 support XMP.
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.
Last edited by XnTriq on Thu Apr 20, 2006 9:30 pm, edited 2 times in total.

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JohnFredC
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Post by JohnFredC » Mon Apr 17, 2006 12:29 pm

Thanks very much for your response!!!

My concern would be inter-application compatibility using XMP functionality with either JPEG2000 or PNG.

I have noticed that choosing "lossless" compression for a JPEG2K image in some applications appears to break compatibility, so I'm expecting to have to experiment a bit with the XMP part.
John

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