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August 2007
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2007.08.21 13:24 "Re: How to support readscanline for strip image and tile image!", by Frank Warmerdam
levinjoe wrote: > Hi: > > Recently, I try to use libtiff to decompress tiff files in > embedded system. For the reason of limited memory(only support at most > 4Mb). So, I have to decompress the original image and scale it down. > > The question is the TIFFReadScanline properly not provided for the tile > image format! And, what is worse, it does not support color system > conversion. > > So, how to use TIFFReadScanline and also let the lib to convert the > image format to ARGB? Levin, As you noted, TIFFReadScanline() just does not support tiled images and it does not do color conversion. So the answer is that you cannot. The TIFFReadRGBAImage() operates on tiled and stripped images and will do color conversion to RGBA format. There are variations of it that work on tile/strip chunks. Libtiff is a relatively low level library tied closely to the TIFF internal organization. It does not provide as high a level of abstraction as you might hope. Sorry, that's just the way it is. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | President OSGeo, http://osgeo.org