How does one add custom metadata tags to an image on the iPhone?

I tried adding custom entries in the exif dictionaries I received from an image. This didn't work. I'm assuming this is due to the fact exif is a standard that is already defined.

Basically I am trying to create a metadata tag that can be placed in jpegs that will have no character limit.

I read that XMP metadata tags do not have character limits. Is this true? If so how would I crea开发者_如何学Cte these on the iPhone?

Thank you.

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I'm not sure what you've all tried code wise, but Caffeinated Cocoa has a pretty good blog entry on Image Metadata that I've used in an application for a client a while ago that might help you.

Also, the SO post Problem setting exif data for an image looks like it references the Caffeinated Cocoa. Although this question is a little over a year old, it still might help.

Try giving these a shot.