The Content API module is a drop-in solution that publishes all of your Drupal content as web APIs. The module includes a full featured administration interface for choosing which content types and fields to publish. Built on top of the Services module, the module provides all you need to publish web APIs without having to do any programming, even as your site structure and content changes over time.
This is a simple module for Drupal 7.x that uses jQuery to transform the TITLE or ALT attribute of a image to a image caption. There is a settings page with lot's of possible configuration.