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From "Charles Matthew Chen" <charlesmc...@gmail.com>
Subject Re: Copying IPTC/EXIF data from one file to another...
Date Mon, 11 Aug 2008 08:59:31 GMT
Hi Christopher,

> IPTC IIM is written by several different tools.  Lightroom and Aperture also
> embed IPTC IIM data into JPEGs, although it's not necessarily binary.  I am
> able to view JPEG files I produced in Lightroom that contain IPTC metadata
> using a hexeditor and my headlines and captions are visible ASCII
> characters.

   IPTC metadata can use a wide variety of charsets for its data; ISO
8859-1,is often used.  This text will be readable in a hex editor.
However, the structure in which they are arranged is binary.


> So ... do both the APP1 and APP13 sections follow the same section format as
> the other sections?  They're started by their section marker, then a 2 byte
> length section, and then the actual data?

   APP1 segments, like other segments begin with a marker and length.
This is followed by a zero-terminated identifier that is used to
distinguish, say, XMP from EXIF data.


> If so, would it be difficult (in your opinion) to read the APP1/APP13
> sections and then drop that raw data on top of another JPEG?  Do you have
> some APIs I could use to possibly do that?  Or does the Sanselan writing
> code only work with Metadata objects (and other higher level concepts)?

   At this point, Sanselan doesn't have any support for handling (ie.
extracting and inserting) arbitrary raw segment data.  The IPTC
support will be structured, ie. it will read and write metadata
models.

Charles

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