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From: "Grissom, Ed" <ed.grissom@intergraph.com>
To: Andy Cave <andy.cave@hamillroad.com>,
        Bob Friesenhahn <bfriesen@simple.dallas.tx.us>, duarte_costa@clix.pt
Subject: RE: [Tiff] Tiff differences
Date: Wed, 2 Feb 2005 11:37:45 -0600 
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According to the original poster, IRasC reads the second image fine, just
slow.  Since I helped write the code, I know that IRasC can read single
strip files, and since the file is uncompressed, it should succeed even with
very large files. 

The basic problem is that IRasC likes to work with tiles, and will be most
efficient when the image is tiled.  In both cases, the internal memory
manager will buffer up 256 or 512 scanlines and then cut those up into tiles
so that the engine can work on them.   The best solution would be to convert
the file to a tiled tiff. 

"Tiff 1" file has 

> MinSampleValue (1 Short): 0
> MaxSampleValue (1 Short): 1

what does this mean ?   Single-bit RGB ?


"Tiff 2" file has 

> RowsPerStrip (1 Short): 31728

Since this is neither the image_length, nor 3 x image_length, nor (-1), I am
not sure what the writer is trying to convey here.  Hmmmm.... it is 3 x the
image_WIDTH.  I'm thinking that this is an error and may have something to
do with the problem. 



D.Costa - you might be able to use the ImageStation Raster Utilities (ISRU)
that comes with IRasC to tile and add overviews to both of these files and
get much better performance.  Failing that, "tiffcp" might be able to at
least "tile" the files.   As far as the "residuals" go, I am not sure what
is causing that error, but it likely has nothing to do with the TIFF format
or this list.  Please contact your Intergraph support person if the
suggestions above do not resolve this issue. 


-- 
ed grissom
ed.grissom@intergraph.com 


> -----Original Message-----
> From: tiff-bounces@remotesensing.org 
> [mailto:tiff-bounces@remotesensing.org] On Behalf Of Andy Cave
> Sent: Wednesday, February 02, 2005 9:44 AM
> To: Bob Friesenhahn; duarte_costa@clix.pt
> Cc: tiff@remotesensing.org
> Subject: Re: [Tiff] Tiff differences
> 
> And fix the tiff writer to put out a page with decent strips.
> 
> I think it's just as much the fault of the writer as it is the
> reader. In this case, as you mention, if the reader can read it
> scanline at a time then it 'could' read it. However, I say
> 'could'. If the reader needed random access to the file, then it
> can't (unless it caches it - which is essentially converting it to a
> degree to a 'strip' based method, even if that's scanline). OK - it
> could in this case 'cause the file is not compressed. However, if it
> were compressed the file would be in the same 'mess'.
> 
> Writing a certain number of strips is so easy, that it's pure
> laziness on the part of the writer in my opinion.
> 
> Anyone who outputs a single strip tiff file should be shot.
> 
> Andy.
> 
> ----- Original Message ----- 
> From: "Bob Friesenhahn" <bfriesen@simple.dallas.tx.us>
> > ...
> >> Any feedback is welcomed in detecting differences that can cause
> >> this issues, as well as the best way to make tiff2 similar to
> >> tiff 1.
> >
> > Use tiffcp to break the problem tiff into one with small strips,
> > or fix the tiff reader to use scanline access when it should.
> >
> > Bob
> > ======================================
> > Bob Friesenhahn
> > bfriesen@simple.dallas.tx.us
> > http://www.simplesystems.org/users/bfriesen
> > _______________________________________________
> > Tiff mailing list
> > Tiff@remotesensing.org
> > http://xserve.flids.com/mailman/listinfo/tiff
> >
> >
> > 
> 
> 
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