APIFlash is used to generate these images.
Set up Image and Caption database objects which contain at least one Image field and one Text field respectively.
Save a user-entered Image and Caption in the database.
Set up a page where the image and caption will be drawn from URL parameters.
Send the user to APIFlash with the above page as a URL parameter, along with an API key, the page width, and the page height. It's recommended that you also use the parameters "delay=2" and "fresh=true" to make sure that the image loads properly.
In the demo app, the width and page height are detected using the Image Metadata plugin, which allows for the output images to be the same dimensions as the input images.