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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Watching this thread with interest. I’ve wanted to do the same, but from python.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#1F497D">-Matt</span><i><span style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#1F497D"><o:p></o:p></span></i></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> gdal-dev <gdal-dev-bounces@lists.osgeo.org>
<b>On Behalf Of </b>Javier Jimenez Shaw<br>
<b>Sent:</b> July 30, 2021 11:19 AM<br>
<b>To:</b> gdal dev <gdal-dev@lists.osgeo.org><br>
<b>Subject:</b> [gdal-dev] Downscaled geotiff with overviews<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Hi<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">I want to make a (power-of-two) downscaled version of a geotiff with overviews efficiently with C++ (not from the console).<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Let's say I have a geotiff with overviews (external or internal), and I want a copy of it, but at 50% of the size. That is just removing the "base" of the pyramid, but keeping
all the other levels. Then voilà, there you have the geotiff 50% smaller, with the overviews already there, almost without any computation. The same for 25% (and any power of 2).<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">However I do not figure out how to do it efficiently in C++. If I understand correctly, CreateCopy is producing an image with the same size. So to downscale I have to create
a new image, read downscaled (that will use the overviews) and write. But later, I have to recreate the overviews on the new image... that are already in the original image.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Is there any way to make it efficiently? (as we have the data there)<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">Thanks.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:10.0pt;font-family:"Calibri",sans-serif">.___ ._ ..._ .. . ._. .___ .. __ . _. . __.. ... .... ._ .__<br>
Entre dos pensamientos racionales <br>
hay infinitos pensamientos irracionales.<o:p></o:p></span></p>
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