Topic: Tag/mark persons on images


I am working on a image upload feature which works great so far. When the images are uploaded I want the users to be able to "tag" persons on pictures (see facebook for example).

Basically I only have to save coordinates, the person(_id) that is on that coordinate in the picture and the image(_id) that it belongs to.

To create those tags there has to be some javascript when the user clicks on the image...

Shouldn't be too hard to implement, but maybe somebody knows some rails plugin or javascript library that comes in handy for that.