Robb,<br><br>If you are using gdal version 1.6 or later, you can use the -ro option[1]. It opens the tiff file in read-only mode and creates external overview.<br><br>[1]: <a href="http://www.gdal.org/gdaladdo.html">http://www.gdal.org/gdaladdo.html</a><br>
<br><div class="gmail_quote">On Mon, Nov 28, 2011 at 11:53 PM, Robb Wright <span dir="ltr"><<a href="mailto:robbkwright@gmail.com">robbkwright@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<br>
I'm working with indexed color types of raster data (charts). The data is in RGB geotiffs and I'm using gdaladdo to create pyramid layers for them. Unfortunately, the best method for this raster type available using gdaladdo is still pretty bad - much of the linework becomes garbled when viewing the pyramids. The best-looking method that I've been able to come up with is:<br>
gdaladdo.exe --config COMPRESS_OVERVIEW DEFLATE -r average<br>
<br>
The Lanczos algorithm method works beautifully when used with other programs - but I need to create .ovr files. gdal_retile.py output looks great - but I can't figure out how to create .ovr files from that output.<br>
<br>
Does anybody know of the availability of the Lanczos resampling method for gdaladdo - or of another way to create .ovr files with Lanczos?<br>
<br>
Robb<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br><br>+91-9494447584<br>17.2416N 80.1426E<br>