[gdal-dev] How to estimate the width/height size of output image in a target CRS without running gdalwarp?

[Bang Pham Huu]

Thanks Even, your suggestion works, I found an example here for Python
that could help others with this powerful feature:
https://gis.stackexchange.com/a/140053/17733


On 05/17/2018 09:02 PM, Even Rouault wrote:
>
> On jeudi 17 mai 2018 11:33:40 CEST Bang Pham Huu wrote:
>
> > Hi,
>
> >
>
> > I have a hard problem to find the width/height of a 2D GeoTiff file
>
> > which is reprojected from a source CRS (e.g: EPSG:4326) to target CRS
>
> > (e.g: EPSG:3857) without running gdalwarp. Because, the file could be
>
> > large (GBs) and I don't need the projected output file, just need the
>
> > width/height of it.
>
> >
>
> > What could be done with gdalwarp is:
>
> >
>
> > gdalwarp  -s_srs EPSG:4326 -t_srs EPSG:3857 full.tif full_3857.tif
>
> >
>
> > gdalinfo full_3857.tif
>
> >
>
> > Size is 879, 811 (width/height).
>
> >
>
> > I've searched a lot and what seems to be good without doing the real
>
> > projection is this gdal function: GDALSuggestedWarpOutput2
>
> >
> https://github.com/OSGeo/gdal/blob/106c8288e7a05f4efc1a588c5a3b2da7ec52d915/
>
> > gdal/alg/gdaltransformer.cpp#L354. However, it doesn't help because my
>
> > application developed in Java and it uses gdal-java (GDAL JNI)
>
> >
> https://search.maven.org/#artifactdetails%7Corg.gdal%7Cgdal%7C1.11.1%7Cpom
>
> > as library. Unfortunately, I cannot find this GDALSuggestedWarpOutput2()
>
> > from gdal-java http://gdal.org/java/overview-summary.html then cannot
>
> > invoke this C++ function from my application to test.
>
> >
>
> > Can anyone please give me a hint to solve this problem?
>
>  
>
> Hi,
>
>  
>
> You can use gdal.AutoCreateWarpedVRT() which will create a in-memory
> warped
>
> VRT without doing the actual warping.
>
>  
>
> http://gdal.org/java/org/gdal/gdal/gdal.html#AutoCreateWarpedVRT-org.gdal.gdal.Dataset-
>
>  
>
> and query the dimensions of the returned Dataset
>
>  
>
> Even
>
>  
>
> -- 
>
> Spatialys - Geospatial professional services
>
> http://www.spatialys.com
>

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