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

Even Rouault even.rouault at spatialys.com
Thu May 17 12:02:16 PDT 2018


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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