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May 2002
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2002.05.13 20:43 "Fwd: Re: tsmAPI and LibTIFF", by Antonio E Scuri
Here is their answer. Any comments? scuri > X-Authentication-Warning: Lomond.AI.SRI.COM: reddy owned process doing -bs > Date: Mon, 13 May 2002 13:02:25 -0700 > From: Martin Reddy <reddy@AI.SRI.COM> > To: "Antonio E. Scuri" <scuri@tecgraf.puc-rio.br> > Subject: Re: tsmAPI and LibTIFF > Organization: SRI International - Artificial Intelligence Center > > > Hi Antonio, > > In the tsmApi, we use a left->right, bottom->top ordering of pixels which is > common in geospatial applications, i.e. the origin is in the bottom-left > corner not the top-left corner. We correctly set the TIFF flags that specify > this so any reader that supports TIFF fully will be able to view the raw > (uncompressed) tiled files and flip them correctly. However, an issue does > arise when using JPEG compression for the data in each tile. JPEG assumes a > top-left origin and so any TIFF viewer will flip each tile. Because we use > TIFF as a storage format for our own terrain data, this is not a big concern > for us and the data is read back correctly by the tsmApi library anyway (and > ultimately by our TerraVision terrain visualization system). > > Cheers, > > Martin. > > > On Mon, 13 May 2002, Antonio E. Scuri wrote: > > Martin, > > > > I noticed that you use the LibTIFF for reading the TIFF images. > > > > I don't know if you guys are aware of a discussion going on in the > > LibTIFF news about the image tiles used by the tsmAPI. In > > http://www.libtiff.org) Check for the "Orientation and Tiled images?" > > thread or go direct to: > > > > > > http://www.remotesensing.org/lists/libtiff_archive/thrd17.html#01633 > > > > > > The images seem to have the tiles in a reversed order. > > > > Best, > > scuri > > > > > > --------------------------------------------------------------------------- > Martin Reddy SRI International, AI Center > Menlo Park, CA 94025-3493 > reddy@ai.sri.com Tel : (650) 859-6468 > http://www.martinreddy.net/ Fax : (650) 859-3735