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<p>Abel,</p>
<p><br>
</p>
<p>there is a subtelty:</p>
<p>a) If bands may have invalid pixels at different locations on
different bands, and that those bands have a different nodata
value, then using GDALRasterBand::SetNoDataValue() is the way to
go.</p>
<p>b) If a given pixel is invalid only if its value on all bands
matches the nodata value on each band, then NODATA_VALUES should
be set instead<br>
</p>
<p><br>
</p>
<p>Example with 2 bands:</p>
<p>- Band 1, NoData=1, pixel_1=1, pixel_2=1<br>
</p>
<p>- Band 2, NoData=2, pixel_1=2, pixel_2=0</p>
<p><br>
</p>
<p>In interpretation a), then pixel_1 and pixel_2 are invalid for
Band 1, and pixel_1 is invalid for Band 2</p>
<p>In interpretation b), then only pixel_1 is invalid (for both
bands)<br>
</p>
<p><br>
</p>
<p><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">Le 21/05/2025 à 08:46, Abel Pau via
gdal-dev a écrit :<br>
</div>
<blockquote type="cite"
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Hello,</div>
<div class="elementToProof"
style="margin-top: 1em; margin-bottom: 1em; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I am implementing a driver that allows different NODATA values
for each band in a dataset.</div>
<div class="elementToProof"
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>From what I understand in the documentation, I should use
the <code>NODATA_VALUES</code> metadata item to document these
values. However, I don't see a clear way to indicate that a
specific band has
<b>no NODATA</b> value within the tuple.</div>
<div class="elementToProof"
style="margin-top: 1em; margin-bottom: 1em; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
On the other hand, the documentation also suggests that <code>NODATA_VALUES</code> is
<b>not widely honoured</b>, which is not very encouraging.</div>
<div class="elementToProof"
style="margin-top: 1em; margin-bottom: 1em; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">
<span style="color: rgb(0, 0, 0);">Therefore, would you consider
it good practice to separate bands with different NODATA
values into separate
</span><span style="color: rgb(200, 38, 19);"><b>sub</b></span><span
style="color: rgb(0, 0, 0);">datasets instead?</span></div>
<div class="elementToProof"
style="margin-top: 1em; margin-bottom: 1em; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Thank you very much for the clarification.</div>
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