I am attempting to pull the EXIF information for images that have values for the EXIF "keywords" attribute. I have successfully read EXIF information using mini_magick by simply opening an image and using:
image["EXIF:Model"]
For some reason, none of the following will return keywords for an image that I know has them:
image["EXIF:Keywords"]
image["EXIF:XPKeywords"]
image["EXIF:Subject"]
I have confirmed that the image in question does have this information using this utility: http://regex.info/exif.cgi
Does mini_magick only have access to certain EXIF values? It seems so odd that I can access certain EXIF information but not others.
EXIF metadata is created by camera, therefore it contains only technical related stuff. What you actually want to access is IPTC and XMP.
Imagemagick, which is behind mini_magick, allows to read IPTC, e.g. image["%[IPTC:2:25]"] for keywords (update: be aware of perfomance issues, see comments).
As for XMP, I don't know an easy way to do this. You can try to run
`identify -verbose #{your_filename}`
and then grub lines that include xmp.