[gdal-dev] Enquiry regarding building of overviews

[lee heng hock]

Hi Even,

Thanks for replying. I am currently using gdal version 1.5.1. I realised
previously the gdal issue i had with building overviews was because I used
external libtiff library. (probably version 3.8). After switching to using
the internally built libtiff library that comes with gdal, everything is
working well.

Thanks alot
Heng Hock


On Wed, Jun 4, 2008 at 1:48 AM, Even Rouault <even.rouault at mines-paris.org>
wrote:

> Hi,
>
> You have to more specific on which GDAL version you are using, whether it
> is
> compiled using internal or external libtiff, the properties of your TIFF
> file. If external libtiff, which libtiff version it is, etc etc. But
> generally, there's no incompatibility between Linux and overview building.
> The same combination of GDAL + libtiff versions should yield the same
> results
> on both Windows and Linux.
>
> If using an "old" GDAL and/or libtiff version, you should also consider
> upgrading to latest GDAL and compiling it with internal libtiff support.
> For
> your information, there were problems with older GDAL&libtiff versions when
> building overviews on TIFF files in compressed formats like LZW or JPEG
> that
> have been solved since then.
>
> Le Tuesday 03 June 2008 11:33:50 lee heng hock, vous avez écrit :
> > hi,
> >
> > I attempted to build overviews for .tiff files on Linux and windows. For
> > the windows version, building of overviews worked fine. But on linux, I
> > have this error message:
> >
> > "ERROR 1: IReadBlock failed at X offset ... "
> >
> > I did a google search and seems to me that this problem is inherent in
> > gdal. Is this problem existent only in Linux but not on windows?
> >
> > Regards
> > Heng Hock
> >
> > On Tue, Jun 3, 2008 at 12:00 AM, <gdal-dev-request at lists.osgeo.org>
> wrote:
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> > > Today's Topics:
> > >
> > >   1. Re: Converting between datum (Bryan Keith)
> > >
> > >
> > > ----------------------------------------------------------------------
> > >
> > > Message: 1
> > > Date: Mon, 2 Jun 2008 08:37:57 -0600 (MDT)
> > > From: "Bryan Keith" <bryan at ideotrope.org>
> > > Subject: Re: [gdal-dev] Converting between datum
> > > To: "Andreas Theofilu" <andreas at theosys.at>
> > > Cc: GDAL list <gdal-dev at lists.osgeo.org>
> > > Message-ID: <2326.64.78.232.178.1212417477.squirrel at ideotrope.org>
> > > Content-Type: text/plain;charset=iso-8859-1
> > >
> > > > Am Sonntag, 1. Juni 2008 14:01:53 schrieben Sie:
> > > >
> > > > Frank, thanks for that hint. It seems to work, but:
> > > >> So, try changing your DataWindow definition to:
> > > >>
> > > >>     <DataWindow>
> > > >>        <UpperLeftX>617400</UpperLeftX>
> > > >>        <UpperLeftY>481865</UpperLeftY>
> > > >>        <LowerRightX>626560</LowerRightX>
> > > >>        <LowerRightY>480365</LowerRightY>
> > > >>        <SizeX>916</SizeX>
> > > >>        <SizeY>150</SizeY>
> > > >>     </DataWindow>
> > > >
> > > > call me stupid, but I can't figure out how you calculated these
> values.
> > > > Allthough I know what square pixel means, I don't know how I can
> > >
> > > calculate
> > >
> > > > them. Could you or anybody else point me to a page where I may find a
> > > > documentation on how to do that?
> > >
> > > Andreas,
> > >
> > > Here you see how to calculate the cellsize from the given numbers:
> > > >>> 481865 - 480365
> > >
> > > 1500
> > >
> > > >>> _ / 150.
> > >
> > > 10.0
> > >
> > > >>> 626560 - 617400
> > >
> > > 9160
> > >
> > > >>> _ / 916.
> > >
> > > 10.0
> > >
> > > So Frank made square cells size 10.0.  In the other direction you need
> to
> > > slightly increase your extent and then calculate the number of pixels
> in
> > > x and y so that you get square cells.
> > >
> > > Bryan
> > >
> > > > --
> > > > Andreas Theofilu
> > > > TheoSys - Software Systems and Solutions
> > > > http://www.theosys.at
> > > > Tel.: +43 676 / 786 53 89
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> > > End of gdal-dev Digest, Vol 49, Issue 4
> > > ***************************************
>
>
>


-- 
Regards
Heng Hock
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