JQuery Progress Circle + fade page?

Using JQuery how would I make the page dim / fade and display a progress circle 开发者_如何学Pythonin the center which is animated? I'd like to do this when the user fills out a form and clicks submit and is awaiting a response.

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I would use the block ui plugin - http://jquery.malsup.com/block/

Then call this before doing the ajax request

$('body').block({ message: '<img src="loading.gif" />' });

And then this is the success method

$('body').unblock();