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
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