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A java library that used over libGdx game framework.
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package com.ng.gdxutils.b2d;

import com.badlogic.gdx.files.FileHandle;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.CircleShape;
import com.badlogic.gdx.physics.box2d.FixtureDef;
import com.badlogic.gdx.physics.box2d.PolygonShape;
import com.badlogic.gdx.utils.Array;
import com.badlogic.gdx.utils.JsonReader;
import com.badlogic.gdx.utils.JsonValue;

import java.util.HashMap;
import java.util.Map;

public class BodyEditorLoader {
	private final Model model;

	// Reusable stuff
	private final Array vectorPool = new Array();
	private final PolygonShape polygonShape = new PolygonShape();
	private final CircleShape circleShape = new CircleShape();
	private final Vector2 vec = new Vector2();

	// -------------------------------------------------------------------------
	// Ctors
	// -------------------------------------------------------------------------

	public BodyEditorLoader(FileHandle file) {
		if (file == null) throw new NullPointerException("file is null");
		model = readJson(file.readString());
	}

	public BodyEditorLoader(String str) {
		if (str == null) throw new NullPointerException("str is null");
		model = readJson(str);
	}

	// -------------------------------------------------------------------------
	// Public API
	// -------------------------------------------------------------------------

	/**
	 * Creates and applies the fixtures defined in the editor. The name
	 * parameter is used to retrieve the right fixture from the loaded file.
	 * 


	 *
	 * The body reference point (the red cross in the tool) is by default
	 * located at the bottom left corner of the image. This reference point
	 * will be put right over the BodyDef position point. Therefore, you should
	 * place this reference point carefully to let you place your body in your
	 * world easily with its BodyDef.position point. Note that to draw an image
	 * at the position of your body, you will need to know this reference point
	 * (see {@link #getOrigin(String, float)}.
	 * 


	 *
	 * Also, saved shapes are normalized. As shown in the tool, the width of
	 * the image is considered to be always 1 meter. Thus, you need to provide
	 * a scale factor so the polygons get resized according to your needs (not
	 * every body is 1 meter large in your game, I guess).
	 *
	 * @param body The Box2d body you want to attach the fixture to.
	 * @param name The name of the fixture you want to load.
	 * @param fd The fixture parameters to apply to the created body fixture.
	 * @param scale The desired scale of the body. The default width is 1.
	 */
	public void attachFixture(Body body, String name, FixtureDef fd, float scale) {
		RigidBodyModel rbModel = model.rigidBodies.get(name);
		if (rbModel == null) throw new RuntimeException("Name '" + name + "' was not found.");

		Vector2 origin = vec.set(rbModel.origin).scl(scale);

		for (int i=0, n=rbModel.polygons.size; i

	 *
	 * The body reference point (the red cross in the tool) is by default
	 * located at the bottom left corner of the image. This reference point
	 * will be put right over the BodyDef position point. Therefore, you should
	 * place this reference point carefully to let you place your body in your
	 * world easily with its BodyDef.position point. Note that to draw an image
	 * at the position of your body, you will need to know this reference point
	 * (see {@link #getOrigin(String, float)}.
	 * 


	 *
	 * Also, saved shapes are normalized. As shown in the tool, the width of
	 * the image is considered to be always 1 meter. Thus, you need to provide
	 * a scale factor so the polygons get resized according to your needs (not
	 * every body is 1 meter large in your game, I guess).
	 *
	 * @param body The Box2d body you want to attach the fixture to.
	 * @param name The name of the fixture you want to load.
	 * @param scale The desired scale of the body. The default width is 1.
	 */
	public void attachFixture(Body body, String name, float scale) {
		RigidBodyModel rbModel = model.rigidBodies.get(name);
		if (rbModel == null) throw new RuntimeException("Name '" + name + "' was not found.");

		Vector2 origin = vec.set(rbModel.origin).scl(scale);

		for (int i=0, n=rbModel.polygons.size; iFor advanced users only. Lets you access the internal model of
	 * this loader and modify it. Be aware that any modification is permanent
	 * and that you should really know what you are doing.
	 */
	public Model getInternalModel() {
		return model;
	}

	// -------------------------------------------------------------------------
	// Json Models
	// -------------------------------------------------------------------------

	public static class Model {
		public final Map rigidBodies = new HashMap();
	}

	public static class RigidBodyModel {
		public String name;
		public String imagePath;
		public final Vector2 origin = new Vector2();
		public final Array polygons = new Array();
		public final Array circles = new Array();
	}

	public static class PolygonModel {
		public final Array vertices = new Array();
		private Vector2[] buffer; // used to avoid allocation in attachFixture()
	}

	public static class CircleModel {
		public final Vector2 center = new Vector2();
		public float radius;
	}

	// -------------------------------------------------------------------------
	// Json reading process
	// -------------------------------------------------------------------------

	private Model readJson(String str) {
		Model m = new Model();

		JsonValue map = new JsonReader().parse(str);

		JsonValue bodyElem = map.getChild("rigidBodies");
		for (; bodyElem != null; bodyElem = bodyElem.next()) {
			RigidBodyModel rbModel = readRigidBody(bodyElem);
			m.rigidBodies.put(rbModel.name, rbModel);
		}

		return m;
	}

	private RigidBodyModel readRigidBody(JsonValue bodyElem) {
		RigidBodyModel rbModel = new RigidBodyModel();
		rbModel.name = bodyElem.getString("name");
		rbModel.imagePath = bodyElem.getString("imagePath");

		JsonValue originElem = bodyElem.get("origin");
		rbModel.origin.x = originElem.getFloat("x");
		rbModel.origin.y = originElem.getFloat("y");

		// polygons
		JsonValue polygonsElem = bodyElem.getChild("polygons");
		for (; polygonsElem != null ;polygonsElem = polygonsElem.next()){

			PolygonModel polygon = new PolygonModel();
			rbModel.polygons.add(polygon);

			JsonValue vertexElem = polygonsElem.child();
			for (; vertexElem != null; vertexElem = vertexElem.next()) {
				float x = vertexElem.getFloat("x");
				float y = vertexElem.getFloat("y");
				polygon.vertices.add(new Vector2(x, y));
			}

			polygon.buffer = new Vector2[polygon.vertices.size];

		}

		// circles
		JsonValue circleElem = bodyElem.getChild("circles");

		for (; circleElem != null; circleElem = circleElem.next()) {
			CircleModel circle = new CircleModel();
			rbModel.circles.add(circle);

			circle.center.x = circleElem.getFloat("cx");
			circle.center.y = circleElem.getFloat("cy");
			circle.radius = circleElem.getFloat("r");
		}

		return rbModel;
	}

	// -------------------------------------------------------------------------
	// Helpers
	// -------------------------------------------------------------------------

	private Vector2 newVec() {
		return vectorPool.size == 0 ? new Vector2() : vectorPool.removeIndex(0);
	}

	private void free(Vector2 v) {
		vectorPool.add(v);
	}
}