[Pmt-exif] Exif keyword for PNG, draft 0.20

[Glenn Randers-P. <gl...@ho...>]

I've posted draft 0.20 of the PNG Exif keyword proposal to
http://pmt.sourceforge.net/exif/drafts/

The separate "eXIF" chunk is eliminated in favor of an image validity
signature contained in the text chunk, which can be used to determine whether
the image has been modified since the Exif data was first written.  There's
also a validity check value for the textual Exif data, so it can be
determined whether someone has changed it.

Glenn