Ah, I was thinking of the old GIF style of terminology:
"Interlacing is also known as "progressive" encoding, because the image becomes progressively clearer as it is received. This terminology is different than the interlaced and progressive scan terminology of video encoding."
According to what I read in the wiki, you would want the interlace.
Quote:
Interlacing is a method of encoding a bitmap image such that a person who has partially received it sees a degraded copy of the entire image. When communicating over a slow communications link, this is often preferable to seeing a perfectly clear copy of one part of the image, as it helps the viewer decide more quickly whether to abort or continue the transmission.
Or
Quote:
There is also an interlaced "Progressive JPEG" format, in which data is compressed in multiple passes of progressively higher detail. This is ideal for large images that will be displayed while downloading over a slow connection, allowing a reasonable preview after receiving only a portion of the data. However, progressive JPEGs are not as widely supported, and even some software which does support them (such as some versions of Internet Explorer) only displays the image once it has been completely downloaded.