What is a “progressive” JPEG?
A progressive JPEG is not a JPEG from Berkeley. It is a JPEG image which has been saved in a way which has rough image data at the beginning of the file, so that a blurry, grainy version of the entire image loads first, coming progressively into focus. This is useful for people with slow internet connections (especially with large images), to allow them to get an idea of what the image is about without waiting for the entire download.
