Thanks for your questions and for your patience in awaiting my response.
I has been some time since I looked at the IPTC standards and I wanted to do a bit of research before responding. It looks like the latest IPTC specifications include a provision for storing metadata in the newer XMP format (in addition to the older Information Interchange Model (IIM) format). According to the PNG standard, XMP metadata can be stored in an image file within an “ancillary chunk” in “iTXt” format.
I have not yet seen a PNG file containing this information and I do not have a tool that will generate a PNG file with it.
If you have one or more PNG files that you believe contain IPTC or XMP metadata I would love to use them to try to add support in MLA. If you can post a link to the files I will investigate further. Thanks for an interesting question and for your interest in the plugin.
It has been seven weeks since the last post in this topic. I am marking it resolved, but please update it if you have any more information on IPTC support in PNG images.
