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<p><span style="font-family:"Calibri",sans-serif;color:black">Hi,<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">I'm doing C++ applications and I'm familiar with GDAL 1.7 C/C++ API. For a new application, I'm switching to GDAL 2.2.<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">In this application, I have the need to extract a region from a raster :<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">Let's say I have 4000px x 4000px elevation raster, covering the whole earth, in EPSG 4326.<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">Now I want to extract the rectangle region between two points (lat_1/long_1) and (lat_2/long_2) in a 128px x 128px tile.<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">I don't want to extract this region in a file, but in memory, to create a data buffer and then work on this buffer with my application.<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">Which is the best/more performant way to do this ?<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">Knowing that :<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"> 1/ the region extraction may need some resampling, so I need to be able to configure the resampling method<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"> 2/ the extracted region boundaries do no necessary fit on exact pixels of the original dataset<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"> 3/ the SRS will not be modified, but I may need a vertical datum shift (EGM96 to WGS84 for example)<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"> 4/ the extraction will be repeated a lot (a lot !) to extract several "tiles" with different bounds : the application can work on really big rasters, so I prefer to avoid complex objects initialization
for each extraction<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">Should I :<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">- create a wrapped dataset (VRTDataSet) and make RasterIO on it ? This seems to solve 1/ and 3/ and 4/, but what about 2/ ?<o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black">- use a WarpOperation and then execute WarpRegionToBuffer method ? <span style="background:white">This seems to solve 1/ and 2/ and 3/, but what about 4/ ?</span><o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black;background:white">Any help will be appreciated.</span><span style="font-family:"Calibri",sans-serif;
color:black"><o:p></o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
<p><span style="font-family:"Calibri",sans-serif;color:black;background:white">Thanks</span><span style="font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
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