Extracting a circle from a raster using GDAL

Question

I can extract a rectangle from a raster using gdalwarp:

gdalwarp -te <x_min> <y_min> <x_max> <y_max> input.tif clipped_output.tif

Is there a way to do this in GDAL using a circle instead of a rectangle?

Rasters tend to be rectangles. However, you can clip a rectangle and burn pixels outside the circle to some fixed value with gdal_rasterize. See gis.stackexchange.com/questions/163371/… — user30184, Commented Dec 12, 2016 at 20:27
@user1186 With gdalwarp, you can do that by using one circular shapefile as 'cut line'. — xunilk, Commented Dec 12, 2016 at 23:27

xunilk · Accepted Answer · 2016-12-12 23:26:42Z

5

With gdalwarp, you can do that by using one circular shapefile as 'cut line'. One syntax of command can be:

gdalwarp -overwrite -dstnodata -999 -cutline your_circular_shape.shp original_raster.tif out.tif

In my particular case, I tried out it with raster DEM and shapefile of next image:

My complete command was:

gdalwarp -overwrite -dstnodata -999 -cutline /home/zeito/pyqgis_data/circle.shp /home/zeito/pyqgis_data/utah_demUTM2.tif /home/zeito/out.tif

and it worked; as it can be observed at the next image (where resulting raster was perfectly aligned with original raster).

answered Dec 12, 2016 at 23:26

xunilk

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thanks @xunilk, I do not have a circle shapefile though. I want to create it based on command line value. Similar to how I do not have a rectangle shapefile but can use gdalwarp to specify bounding box. Is there a command to create the circle shapefile?
– user1186
Commented Dec 12, 2016 at 23:30
1

There are two parameters ( '-cwhere expression' and '-csql query'). You can try them (see documentation in: gdal.org/gdalwarp.html).
– xunilk
Commented Dec 12, 2016 at 23:46
thanks @xunilk, I would really appreciate if you have any example or could point me to one.
– user1186
Commented Dec 13, 2016 at 0:19
1

There is no way around using a separate datasource file when using gdalwrap. Both -cwhere and -csql require a -cutline to be defined in the first place. However, it probably is very easy to simply generate a temporary circle.shp for this purpose that you discard afterwards. If you want more help with that, please edit your question and provide more details regarding data structure and scripting environment.
– Senshi
Commented Dec 13, 2016 at 8:18

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