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Hi all,</div>
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I retiled whole lot of imagery over the weekend using the following gdal_retile command:</div>
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<p style="margin: 0px; font-size: 12px; font-family: Courier;">gdal_retile.py -v -r bilinear -levels 8 -ps 2048 2048 -s_srs EPSG:28355 -co "TILED=YES" -co "ALPHA=YES" -targetDir ~/output ~/input/*.tif</p>
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<div style="font-family: Calibri, sans-serif; font-size: 14px;">The result was good until I realised all the areas that should be transparent were instead black. It seems the problem is the source imagery didn’t have an alpha channel; it didn’t need one as
there was no transparent data to represent. Because the source imagery didn’t fill the entire extent, gdal_retile had to create loads of transparent and partially-transparent tiles, which of course wound up black.</div>
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<div><font face="Calibri,sans-serif">I was under the impression that "</font><font face="Courier"><span style="font-size: 12px;">-co ALPHA=YES</span></font><font face="Calibri,sans-serif">” would instruct gdal_retile to generate an alpha channel for all the
generated tiles. Is this a bug? If not, how do I otherwise instruct </font><font face="Calibri,sans-serif">gdal_retile to generate an alpha channel when required?</font></div>
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<div><font face="Calibri,sans-serif">I’m working around this by using gdal_translate to re-save the source imagery with an (empty) alpha channel, so gdal_retile now outputs transparent tiles. </font></div>
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<div><font face="Calibri,sans-serif">Any feedback is appreciated.</font></div>
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<p class="MsoNormal" style="color: rgb(0, 0, 0); margin: 0cm 0cm 0.0001pt;">Cheers,</p>
<p class="MsoNormal" style="color: rgb(0, 0, 0); margin: 0cm 0cm 0.0001pt;">Tom</p>
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<o:p> </o:p></p>
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