**TestBuilder**and the

**TestRunner**.

- The
**TestBuilder**is a GUI tool with many powerful capabilities for loading, editing and visualizing geometry. It also provides the ability to run numerous geometric functions which expose (and in some cases enhance) the JTS library functionality. - The
**TestRunner**is a command-line tool which runs tests in the JTS XML test format.

But there's a gap which these two tools don't fill. It's often required to run JTS operations on geometry data for purposes of testing, debugging or timing operations. This

*can*be done in the TestBuilder, but being a GUI it's highly manual process, and tedious to repeat multiple times. It is (just) possible to use the TestRunner for this, but that introduces the awkwardness of wrapping the input data in XML. The only other option up until now was to write a Java program, which is overkill for quick tests, and not very accessible for some.
What's really needed is a JTS equivalent of the UNIX expr. It should have the ability to accept geometry inputs, run an operation on them, and output the results. (Another comparison might be to a

*very*small subset of**GDAL/OGR**, focussed on geometry only - and of course running in Java).
The TestBuilder already provides a rich framework for most of this functionality, so it turned out to be simple to expose this as a command-line tool. Behold - the jtsop command!

jtsop has the following capabilities:

- read geometries from files or command-line
- input formats include WKT, WKB, GeoJSON, GML and SHP
- execute any TestBuilder operation on the geometry input (which includes all JTS Geometry methods)
- output the result as WKT, WKB, GeoJSON, GML or SVG
- report metrics for geometry and execution times
- dynamically load and run geometry functions provided in external Java classes

**Examples**

Compute the area of a WKT geometry and output it as text

jtsop -a some-geom.wkt -f txt area

Compute the unary union of a WKT geometry and output as WKB

jtsop -a some-geom.wkt -f wkb Overlay.unaryUnion

Compute the union of two geometries in WKT and WKB and output as WKT

jtsop -a some-geom.wkt -b some-other-geom.wkb -f wkt Overlay.Union

Compute the buffer of distance 10 of a WKT geometry and output as GeoJSON

jtsop -a some-geom.wkt -f geojson Buffer.buffer 10

Compute the buffer of a literal geometry and output as WKT

jtsop -a "POINT (10 10)" -f wkt Buffer.buffer 10

Output a literal geometry as GeoJSON

jtsop -a "POINT (10 10)" -f geojson

Compute an operation on a geometry and output only geometry metrics and timing

jtsop -v -a some-geom.wkt Buffer.buffer 10

**Uses**

jtsop is already proving its worth in the JTS development process. Some other use cases come to mind:

- Converting geometry between formats (e.g. WKT to GeoJSON)
- Filtering and extracting subsets of geometry data (there are various selection functions available to do this)
- Computing summary statistics of geometry data

**Further Work**

There's some interesting enhancements that could be added:

- provide options to refine the input such as spatial filtering or geometry type coercion
- allowing chaining multiple operations together using a little DSL (this is possible via shell piping, but doing this internally would be more efficient). This could use the pipe operator a la Elixir.
- Include the
**Proj4J**library to allow coordinate system conversions (this can be done now as a simple extension using the dynamic function loading, but it would be nice to have it built in) - output geometry as images (using the TestBuilder rendering pipeline)

## 2 comments:

Hello,I came across a buffer problem in JTS:the polygon buffer is very slowly.In the post(http://blog.cleverelephant.ca/2008/07/buffering-jujutsu.html)，the author refered "Martin Davis tried out a variant of simplification, and produced results even faster than Michaël’s.".But,the link is broken.Is there any backup or where can i find the method？fully appreciated!

The buffer simplification method is implemented in JTS.

If you need more help best to post to the JTS mailing list.

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