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January 2007
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2007.01.17 17:28 "Re: Elevation Data", by Joris Van Damme
Frank, Frank Warmerdam wrote: > I'm not sure where progressive streaming came into this. My OpenEV > viewer already does dynamic sampling of non-8bit TIFF files and > automatic contrast stretch. It doesn't require too much extra time, > and it provides excellent quick display of a wide variety of > scientific data, including elevation data. > ... > I disagree that dynamic scaling is impractical for large > images. In my (prejudice, on-track and very limited) mind, large image handling is pipeline-based. If I need to render a large TIFF (or any TIFF for that matter), I set up a pipeline that decodes, resamples, and converts color and all. I next start pulling the pipeline, and as results come in, I progressively update display. That's just one very typical example, of course, of what I regard 'progressive streaming' of imaging processes. But it's sufficient to explain the dynamic sampling is rather awkward in this situation. I'd have to set up a first pipeline that decodes and gathers range, and run the complete pipeline, before I'd be able to set up the second pipeline with the detected range in the color conversion steps. For huge images, that's many seconds before the second pipeline is even build, which conflicts with my need to start progressive build-up of display asap. The keyword here is not *my* needs, of course. The point I'm making, is that it conflicts with *some* needs, and the given example is taken from my own experience only because that's closest at hand. > There is a certain inherent tension between those who think of TIFFs > and images in general in photometric terms, and those who think of > them as a container for transporting all sorts of gridded scientific > data. But we need to recognize they are both legitimate applications. Yes, that is very true. And I hope to be all ears and try and understand the applications and needs I'm less familiar with. Best regards, 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