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June 2011
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2011.06.30 20:35 "Re: Is it possible to read a large tiff image in portions?", by David Burken
Hi, On 06/30/2011 04:16 PM, Hib Eris wrote: > Hi David, > > On Thu, Jun 30, 2011 at 6:02 PM, David Burken<dburken@comcast.net> wrote: >> On 06/30/2011 11:21 AM, Hib Eris wrote: >>> To avoid this, I would like to read and process the image in pieces, >>> how should I do this with libtiff? >>> >> I'll point you to an example. Ossim is tile based under the hood. So all >> of our image readers have one purpose, to stuff a tile of image data like >> 256x256. Since tiff can be many flavors I'd start at >> ossimTiffTileSource::getTile as it takes multiple paths. >> >> http://trac.osgeo.org/ossim/browser/trunk/ossim/src/ossim/imaging/ossimTiffTileSource.cpp > Thanks for the example. It seems to me that there is no higher level > function in libtiff to accomplish what I want and that most people > solve this by resorting to using low level functions like > TIFFReadScanline(), TIFFReadEncodedStrip(), and TIFFReadTile(). > > I would like to avoid that. Using those functions means putting > knowledge about the tiff format into my application. I would like to > keep my application simple, I am no tiff expert and I would like to > shield myself and other maintainers of my application from any tiff > specification intrinsics. In my opinion, libtiff is the place for tiff > expertise, not in the applications using it. > > Wouldn't it be a good idea to implement a function like > ossimTiffTileSourcce::getTile in libtiff? > Maybe call it TIFFReadRGBARectangle(). It seems lots of applications > could benefit from it. > > Hib > That would be a good addition. All the higher level libraries that link with libtiff write their own(like ossim) so it would save a lot of duplicate code. Tiff's come in many flavors though... The low levelness of libtiff is a good thing, i.e. small, portable, fast, but as you bring up it lack some things. I'm not sure how you'd start to get that accepted in the library. I guess this mailing list maybe. I'd vote for it... Take care, Dave