<div dir="ltr">Wow. Can't believe I missed the middle one, at least. Thank you, Even, as always!<div><br></div><div>Simon</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, May 3, 2024 at 3:03 PM Even Rouault <<a href="mailto:even.rouault@spatialys.com">even.rouault@spatialys.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<p>==> <span><span></span></span><span><span><span>GDALCreateApproxTransformer</span></span></span><span>(): </span><a href="https://gdal.org/api/gdal_alg.html#_CPPv427GDALCreateApproxTransformer19GDALTransformerFuncPvd" target="_blank">https://gdal.org/api/gdal_alg.html#_CPPv427GDALCreateApproxTransformer19GDALTransformerFuncPvd</a></p>
<p>Otherwise there's <span></span><span><span><span>OGRCoordinateTransformation</span></span></span>::<span><span><span>TransformBounds</span></span></span><span></span>(), but this works from a rectangle in
the source CRS</p>
<p>Most simple would be to use <span></span><span><span><span>GDALAutoCreateWarpedVRT</span></span></span><span>()
(<a href="https://gdal.org/api/gdalwarp_cpp.html#_CPPv423GDALAutoCreateWarpedVRT12GDALDatasetHPKcPKc15GDALResampleAlgdPK15GDALWarpOptions" target="_blank">https://gdal.org/api/gdalwarp_cpp.html#_CPPv423GDALAutoCreateWarpedVRT12GDALDatasetHPKcPKc15GDALResampleAlgdPK15GDALWarpOptions</a>)
to EPSG:4326 and just take the extent of the warped VRT.</span></p>
<div>Le 03/05/2024 à 23:25, Simon Eves via
gdal-dev a écrit :<br>
</div>
<blockquote type="cite">
<div dir="ltr">I like it.</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, May 3, 2024 at 2:24 PM
Javier Jimenez Shaw <<a href="mailto:j1@jimenezshaw.com" target="_blank">j1@jimenezshaw.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div>Now I think I understand what you mean.</div>
<div>One effective way is to convert the four sides of the
image. To avoid the conversion of every pixel, you can
start a partition process. Then compare the difference
between the transformed central point and just the mid
point between the extremes. If that different is bigger
than an certain threshold, keep subdividing each side.
With that you have a good approximation of the borders of
the image transformed, and then you can compute your
bounding box.</div>
<div>The idea is not mine. Even Rouault mentioned it last
year in FOSS4G. IIRC, it is used by gdalwarp to not
reproject every single point; once the subdivision is
enough, then it does linear interpolation.<br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, 3 May 2024 at
22:18, Simon Eves <<a href="mailto:simon.eves@heavy.ai" target="_blank">simon.eves@heavy.ai</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Yes, but that's just the corners.
<div><br>
</div>
<div>Consider, say, a raster that contains a satellite
sweep which is not axis-aligned but forms a
"windshield wiper" shape in lon/lat space. The
bounding box of ALL the pixels is not just the
bounding box of the corners.</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, May 3, 2024 at
1:09 PM Javier Jimenez Shaw <<a href="mailto:j1@jimenezshaw.com" target="_blank">j1@jimenezshaw.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="auto">Maybe I don't understand your
question, but in gdalinfo you have the four corners
as lat-lon</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, 3 May
2024, 21:46 Simon Eves via gdal-dev, <<a href="mailto:gdal-dev@lists.osgeo.org" target="_blank">gdal-dev@lists.osgeo.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">So we are trying to optimize our
raster import process, and particularly the
steps to derive the final WGS84/4326 bounding
box for a raster file or tile thereof.
<div><br>
</div>
<div>Obviously in the general case, the
transform is from integer pixel coordinate
through the Affine Transformation matrix and
then whatever OGRCoordinateTransformation is
required to get to WGS84/4326, and perhaps a
GCP-based mesh transformation too.</div>
<div><br>
</div>
<div>Currently we are deriving the bounding box
by passing all pixels of the four edges of the
file/tile through the full transform, except
in the simple Affine-only case where we just
transform the four corners.</div>
<div><br>
</div>
<div>Is there any shortcut API provided by GDAL
or PROJ to allow the bounding box to be
computed (or at least safely over-estimated)
in the general case? I'm assuming that even a
non-GCP OGRCT could still be non-linear such
that just transforming the corners is
insufficient.</div>
<div>
<div><br>
</div>
<div>Thanks in advance,</div>
<div><br>
</div>
<div>Simon</div>
<div><br>
</div>
<span class="gmail_signature_prefix">-- </span><br>
<div dir="ltr" class="gmail_signature">
<div dir="ltr">Simon Eves
<div>Senior Rendering Engineer</div>
<div>+1 (415) 902-1996<br>
<a href="mailto:simon.eves@heavy.ai" rel="noreferrer" target="_blank">simon.eves@heavy.ai</a></div>
<div><span>
<p dir="ltr" style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><a href="http://www.heavy.ai" rel="noreferrer" target="_blank"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(17,85,204);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"><span style="border:medium;display:inline-block;overflow:hidden;width:156px;height:29px"><img style="margin-left: 0px; margin-top: 0px;" width="156" height="29"></span></span></a></p>
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