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August 2006
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2006.08.30 19:48 "Re: TIFF Interlacing", by Joris Van Damme
Bob, Bob Friesenhahn wrote: > On Tue, 29 Aug 2006, Jeffrey Glenn wrote: > > Does TIFF support interlacing? Like...in the way JPEG 2000 does? I've no clue where your quote from, I seem to have missed the message to which you're replying. One could ask what interlacing is really useful for. The typical example is an JPEG or PNG file coming in through a slow medium. The big advantage of interlacing, is that software can show an approximation of the complete image in a very early state, building on just the first few part of the image file when they came in already. (The term 'interlacing' is also used in different context, but I'm guessing that's not relevant here.) Thus, it seems like interlacing makes sense in streaming file formats. TIFF is not a streaming file format, but a random-access file format. As such, I feel interlacing is a bit out of place, but adding downsampled SubIFDs to an image would make perfect sense as it covers the equivalent functionality translated to the random-access realm: the big advantage of downsampled SubIFDs, is that software can show an approximate of the complete image much faster, with much less IO and processing cost. This equivalent works even if you're dealing with a slow medium with some random-access supporting communication protocol or something. I'm thinking that's the natural reason that interlacing just didn't 'grow' in TIFF, while the SubIFDs tag did. Joris Van Damme info@awaresystems.be http://www.awaresystems.be/ Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html