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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:#222222;background:white;mso-ligatures:none">Hi,</span><span style="mso-ligatures:none"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none">I'm experiencing a strange issue I've never seen before where certain resampling methods that should only include values in the original
dataset, like mode and nearest, are adding new values in the overviews. <o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none">For example, the original raster contains the following values:<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none">[0, 1, 2, 4, 5, 8, 9, 10, 16, 17, 18, 20, 21, 32, 33, 34, 36, 37, 40, 41, 42, 64, 65, 66, 68, 69, 72, 73, 74, 80, 81, 82, 84, 85]<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none">I resample it using the following command:<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none">gdalwarp dataset.tif dataset_cog.tif -of COG -co COMPRESS=LZW -r mode<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif;color:#222222;mso-ligatures:none">And when I look at overviews, I start these values, especially as it downsamples further:<br>
<br>
[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 90, 91]<br>
<br>
I saw the same if I tried it with nearest resampling. Maybe I'm misunderstanding, but I would think these resampling methods would retain the original values, and not interpolate any in-between values. <br>
<br>
I'm using GDAL version 3.9.1 on Mac M3 from Homebrew. <br>
<br>
Thanks,<br>
Justin<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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