Does progressive JPEG require chunked transfer encoding?

I've been looking at how to implement an API over HTTP that allows for online processing of the resource it returns. This resource could be a progressive JPEG, for example. In reading up on progressive JPEGs and how they are rendered in browsers I never see any mention of this requiring chunked transfer encoding to work. If I'm understanding things correctly I don't see how progressive JPEGs could be rendered before they are fully downloaded without the use of chunked transfer encoding. Is this correct?