gdal_contourf

Generates filled contours (polygons) from raster data. It runs on the
JVM and is optimized for speed. A large raster can typically be processed in a
matter of seconds. It uses GDAL to read raster files and
write vector files. Contours are generated using the
Marching Squares algorithm.

Note that as of GDAL v2.4.0,
gdal_contour can produce
polygons using the -p option, but it is very slow.

Requirements

• Java
• GDAL
• GDAL Java bindings (libgdal-java on Debian/Ubuntu, gdal-java on Fedora/Centos)

Building

Make sure the GDAL version in build.gradle.kts matches the system version. (ie. 3.0.0)

./gradlew shadowJar

Usage

It can be used as a library with Gradle:

repositories {
    jcenter()
    maven("https://jitpack.io")
}
dependencies {
    implementation("com.github.brewin:gdal_contourf:1.1.2")
}

Or run from the command line:

java -jar gdal_contourf-1.1.2_gdal-3.0.0.jar --in input.tif --band 1 \
    --levels -50 0 50 100 150 --simplification 30 --epsg 4326 \
    --format GeoJSON --out output.geojson

Disclaimer

This is not well-tested and probably never will be. It works for my use-case.
Correctness not guaranteed.