How can I add the featured image functionality to a custom taxonomy?

I would like to be able to use the ‘featured image’ functionality, found on post types, for a custom taxonomy.

I have a taxonomy called ‘collections’ and I would like each collection to have a featured image. I will then use the featured image in a custom template that will show all of the collection, their titles and featured images.

I need the uploaded image to be resized into the custom image sizes that I have set in my theme.

There is a similar question here: Can I set a default featured image for a category? However, the top answer won’t work for me, and I can’t rely on a plugin.

Can anyone help?

Many thanks,

Keith

It’s a little complex, but you can add custom meta to taxonomies. http://pippinsplugins.com/adding-custom-meta-fields-to-taxonomies/

You could pretty easily integrate a WP media uploader field that would allow you to enter an image into the field.