Michal ZimmermannPieces of knowledge from the world of GIS.

Clip Raster With Vector Using GDAL

Recently I needed to clip several raster files with polygonal layer of municipalities. A solution to this task is pretty straightforward using GDAL and a bit of Bash and QGIS thrown in.

The necessary steps are:

  1. Put each polygon to a separate file. This can be done easily with Vector - Data Management Tools - Split Vector Layer in QGIS. The solution below assumes that each shapefile has the same basename as the raster file.
  2. These polygons are stored in the obce subfolder relative to the folder with rasters.
  3. An output folder exists that is used for… output, yes.
  4. Rasters are saved with output alpha band for nodata (-dstalpha flag).
  5. The script takes one argument - raster name.
  6. Profit!
#!/usr/bin/env bash

BASE=$(basename $OBEC _jpeg.tif)
echo $BASE
EXTENT=$(ogrinfo -so obce/${BASE}.shp $BASE | grep Extent \
| sed 's/Extent: //g' | sed 's/(//g' | sed 's/)//g' \
| sed 's/ - /, /g')
EXTENT=$(echo $EXTENT | awk -F ',' '{print $1 " " $4 " " $3 " " $2}')
gdal_translate -projwin $EXTENT -of GTiff $OBEC output/${BASE}.tif
gdalwarp -dstalpha -s_srs 'EPSG:5514' -t_srs 'EPSG:5514' \
    -co TILED=YES -\
    of GTiff \
    -cutline obce/${BASE}.shp \
    output/${BASE}.tif output/${BASE}.final.tif

Note that if gdalwarp doesn’t recognize an EPSG code (which is the case for my country national grid), you might pass it as a PROJ.4 string.

According to the point 5 in the above list, the script needs to be run in a loop:

for f in *_jpeg.tif;
    do the_script_above.sh $f