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<div class="moz-cite-prefix">PS. gdalwarp offers more flexibility
when mosaicing rasters, and is better at memory management. I have
just noticed that in GDAL 1.10 and above there is an gdalwarp
option -setci that 'Sets the color interpretation of the bands of
the target dataset from the source dataset'. This could be used to
remove the assignment of the alpha channel to the IR band on
merging. Sadly there isn't an example of its usage!<br>
<br>
Cheers,<br>
<br>
Andy<br>
<br>
On 02/12/2013 11:53, Jonathan Moules wrote:<br>
</div>
<blockquote
cite="mid:CAA-xNcWfLo690+cRA-zo5Ki+z4tE9mSMcrNzrVpOfhQJ+55PZg@mail.gmail.com"
type="cite">
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<div dir="ltr">Hi List,
<div>I've got a 4 band raster aerial photography (RGBI) that
comprises lots of tiles. I've merged some of the tiles
together with:</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">gdal_merge
-o 1.tif -of GTiff -co TILED=YES -co BIGTIFF=YES -co
COMPRESS=JPEG -co JPEG_QUALITY=50 -co BLOCKXSIZE=512 -co
BLOCKYSIZE=512 --optfile tiff_list.txt</blockquote>
<div><br>
</div>
<div>But the resultant file looks funny in QGIS.</div>
<div>This is what the source file looks like (correct):</div>
<div><img src="cid:part1.07000308.08000801@geodata.soton.ac.uk"
alt="Inline images 1"><br>
</div>
<div><br>
</div>
<div>This is what the merged file looks like (wrong):</div>
<div><img src="cid:part2.06060802.07090904@geodata.soton.ac.uk"
alt="Inline images 2"><br>
</div>
<div><br>
</div>
<div>All the shadows are a whitey colour. This doesn't happen
with 3-band (RGB) images.</div>
<div>I've tried comparing individual bands; they all look
different in the 4-band.</div>
<div><br>
</div>
<div>However, if I open the four-band in ArcGIS, it looks fine
(both source and original).</div>
<div><br>
</div>
<div>Anyone know what's going on? Is it a QGIS bug or is it
doing something "smart"; I can't see anything odd going on
with symbology.<br>
</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Jonathan</div>
</div>
<br>
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<br>
<br>
<pre class="moz-signature" cols="72">--
Andy Harfoot
GeoData Institute
University of Southampton
Southampton
SO17 1BJ
Tel: +44 (0)23 8059 2719
Fax: +44 (0)23 8059 2849
<a class="moz-txt-link-abbreviated" href="http://www.geodata.soton.ac.uk">www.geodata.soton.ac.uk</a>
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