Zoltan,<br><br>Have you tried the nearblack GDAL utility on the original 176 images?<br><a href="http://www.gdal.org/nearblack.html">http://www.gdal.org/nearblack.html</a><br><br><div class="gmail_quote">On Wed, Feb 16, 2011 at 5:25 PM, Zoltan Szecsei <span dir="ltr"><<a href="mailto:zoltans@geograph.co.za">zoltans@geograph.co.za</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;"><div class="im">On 2011-02-16 12:20, Zoltan Szecsei wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Hi All,<br>
I've built a vrt with 176 images.<br>
<br>
I now need to mosaic this whole area into roughly 5 x 5 ortho images.<br>
<br>
How can I force the white edges into background of the overlapping orthos?<br>
I'm a little cautious of simply (finding a way to) making "white" transparent as it is only the white on the edges that need to be backgrounded.<br>
</blockquote>
<br></div>
Hi again,<br>
Since the above post, I have tried different ways to set nodata, but to no avail - I still get the white edges:<br>
(see jpeg sent with my original post)<br>
<br>
gdalbuildvrt -addalpha -hidenodata -input_file_list files 177_untiled_orthos_nodata.vrt<br>
gdalbuildvrt -srcnodata "0 0 0" -addalpha -hidenodata -input_file_list files 177_untiled_orthos_blk.vrt<br>
gdalbuildvrt -srcnodata "255 255 255" -addalpha -hidenodata -input_file_list files 177_untiled_orthos_white.vrt<br>
<br>
How should I be masking out the nodata (or even white pixels) so that when I mosaic a bunch of tiffs together, I dont get the white stripes in the resulting image?<br>
<br>
Using GDAL 1.7.3, released 2010/11/10 on Ubuntu 10.04<br>
Viewing with Quantum GIS - 1.6.0-Trunk on Ubuntu 10.04 (same box).<br>
...but running the whole lot in xterms with Xming & putty from my WinVista box.<br>
<br>
<br>
Regards,<div class="im"><br>
Zoltan<br>
<br>
<br>
<br>
<br>
-- <br>
<br>
===========================================<br>
Zoltan Szecsei PrGISc [PGP0031]<br>
Geograph (Pty) Ltd.<br>
P.O. Box 7, Muizenberg 7950, South Africa.<br>
<br>
65 Main Road, Muizenberg 7945<br>
Western Cape, South Africa.<br>
<br>
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<br>
Tel: +27-21-7884897 Mobile: +27-83-6004028<br>
Fax: +27-86-6115323 <a href="http://www.geograph.co.za" target="_blank">www.geograph.co.za</a><br>
===========================================<br>
<br>
<br>
<br></div>
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</blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9494447584<br>17.2416N 80.1426E<br>