Re: Registratiion of XML:com.adobe.xmp PNG iTXt chunk keyword

On Sat, Jan 14, 2017 at 7:59 PM, Glenn Randers-Pehrson
<[email protected]> wrote:
> Our 2009 discussion ended with Cosmin's proposal:
>
>   It is proposed to register the following new text keyword for
>   use in PNG files:
>
>   XML:com.adobe.xmp
>   Extensible Metadata Platform (XMP) information, formatted
>   as required by the XMP specification [XMP].  The use of iTXt,
>   with Compression Flag set to 0, and both Language Tag and
>   Translated Keyword set to the null string, are recommended
>   for XMP compliance.
>
>   References
>   [XMP]
>      Adobe Systems Inc., "XMP Specification", September 2005.
>      http://www.adobe.com/devnet/xmp/

I think it is enough to just reference the Adobe document (see my
other post).   I don't know what pngcrush does with text chunks but I
see nothing in the PNG specification which would prevent a "PNG
optimizer" from taking a text chunk and altering the compression or,
indeed, the format.  In particular a valid XMP packet need not contain
anything other than ASCII characters so could easily be converted to
zTXt or tEXt.

-- 
John Bowler <[email protected]>
+1 (541) 450-9885
PO BOX 3151
KERBY OR 97531-3151
USA

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