VmlPathDecoder.java

/*
 * This is part of Geomajas, a GIS framework, http://www.geomajas.org/.
 *
 * Copyright 2008-2015 Geosparc nv, http://www.geosparc.com/, Belgium.
 *
 * The program is available in open source according to the GNU Affero
 * General Public License. All contributions in this program are covered
 * by the Geomajas Contributors License Agreement. For full licensing
 * details, see LICENSE.txt in the project root.
 */

package org.geomajas.gwt.client.gfx.context;

import org.geomajas.geometry.Coordinate;
import org.geomajas.gwt.client.spatial.geometry.Geometry;
import org.geomajas.gwt.client.spatial.geometry.LineString;
import org.geomajas.gwt.client.spatial.geometry.LinearRing;
import org.geomajas.gwt.client.spatial.geometry.MultiLineString;
import org.geomajas.gwt.client.spatial.geometry.MultiPolygon;
import org.geomajas.gwt.client.spatial.geometry.Polygon;

/**
 * <p>
 * Decoder for geometry objects, that transforms them into strings that can be used as the "d" attribute of VML path
 * elements.
 * </p>
 * 
 * @author Pieter De Graef
 */
public final class VmlPathDecoder {

	private VmlPathDecoder() {
	}

	/**
	 * This function decodes a Geometry (line or polygon) to a path's d-attribute.
	 * 
	 * @param geometry
	 *            The geometry to be decoded into a single path D attribute.
	 * @return The D attribute value as a string.
	 */
	public static String decode(Geometry geometry) {
		return decode(geometry, 1.0f);
	}

	/**
	 * This function decodes a Geometry (line or polygon) to a path's d-attribute.
	 * 
	 * @param geometry
	 *            The geometry to be decoded into a single path D attribute.
	 * @param scale
	 *            A scale value to apply on all the coordinates of the geometry before decoding.
	 * @return The D attribute value as a string.
	 */
	public static String decode(Geometry geometry, float scale) {
		if (geometry == null) {
			return "";
		}
		if (geometry instanceof LinearRing) {
			return decodeLinearRing((LinearRing) geometry, scale);
		} else if (geometry instanceof LineString) {
			return decodeLine((LineString) geometry, scale);
		} else if (geometry instanceof Polygon) {
			return decodePolygon((Polygon) geometry, scale);
		} else if (geometry instanceof MultiPolygon) {
			return decodeMultiPolygon((MultiPolygon) geometry, scale);
		} else if (geometry instanceof MultiLineString) {
			return decodeMultiLine((MultiLineString) geometry, scale);
		}
		return "";
	}

	// -------------------------------------------------------------------------
	// Private functions:
	// -------------------------------------------------------------------------

	/**
	 * Convert {@link LineString} to a VML string.
	 * 
	 * @param line
	 *            line to convert
	 * @param scale
	 *            scale to use
	 * @return vml string representation of linestring
	 */
	private static String decodeLine(LineString line, float scale) {
		if (line == null || line.isEmpty()) {
			return "";
		}
		StringBuilder buffer = new StringBuilder();
		addCoordinates(buffer, line.getCoordinates(), scale);
		buffer.append(" e ");
		return buffer.toString();
	}

	private static void addCoordinates(StringBuilder buffer, Coordinate[] coordinates, float scale) {
		buffer.append(" m ");
		buffer.append(parseValue(scale * coordinates[0].getX()));
		buffer.append(",");
		buffer.append(parseValue(scale * coordinates[0].getY()));
		buffer.append(" l");
		for (int i = 1; i < coordinates.length; i++) {
			buffer.append(" ");
			buffer.append(parseValue(scale * coordinates[i].getX()));
			buffer.append(",");
			buffer.append(parseValue(scale * coordinates[i].getY()));
		}
	}

	private static String decodeLinearRing(LinearRing linearRing, float scale) {
		if (linearRing == null || linearRing.isEmpty()) {
			return "";
		}
		StringBuilder buffer = new StringBuilder();
		addCoordinates(buffer, linearRing.getCoordinates(), scale);
		buffer.append(" x ");
		return buffer.toString();
	}

	private static String decodeMultiLine(MultiLineString multiLine, float scale) {
		int n = multiLine.getNumGeometries();
		StringBuilder pstr = new StringBuilder();
		for (int i = 0; i < n; i++) {
			pstr.append(decodeLine((LineString) multiLine.getGeometryN(i), scale));
		}
		return pstr.toString();
	}

	private static String decodePolygon(Polygon polygon, float scale) {
		if (polygon == null || polygon.isEmpty()) {
			return "";
		}
		StringBuilder pstr = new StringBuilder();
		pstr.append(decodeLinearRing(polygon.getExteriorRing(), scale));
		for (int i = 0; i < polygon.getNumInteriorRing(); i++) {
			pstr.append(decodeLinearRing(polygon.getInteriorRingN(i), scale));
		}
		return pstr.toString() + " e";
	}

	private static String decodeMultiPolygon(MultiPolygon multipoly, float scale) {
		StringBuilder pstr = new StringBuilder();
		for (int i = 0; i < multipoly.getNumGeometries(); i++) {
			pstr.append(decodePolygon((Polygon) multipoly.getGeometryN(i), scale));
		}
		return pstr.toString();
	}

	private static int parseValue(double value) {
		if (value > 21600) {
			return 21600;
		} else if (value < -21600) {
			return -21600;
		}
		return (int) Math.round(value);
	}
}