Which function handles IPTC data?

Maybe one of these plugins could be revealing?

http://wordpress.org/extend/plugins/tags/iptc

http://codex.wordpress.org/Function_Reference/wp_read_image_metadata

LOL is it “cool” to look into plugins to solve coding problems?

Check the license. I do believe all listed here can be…
https://codex.wordpress.org/Writing_a_Plugin#License

Code publicly released is fair game…In fact many of the plugins build off other plugins and many of the themes include plugin code – properly acknowledging the original author is done (usually).