Began fixing bugs with caused by asynchronous listener calls.

#bug

src/main/java/seng302/visualiser/map/Boundary.java

@@ -0,0 +1,44 @@
+package seng302.visualiser.map;
+
+/**
+ * The Boundary class represents a rectangle territorial boundary on a map. It
+ * contains four extremity double values(N, E, S, W). N and S are represented as
+ * latitudes in radians. E and W are represented as longitudes in radians.
+ *
+ * Created by Haoming on 10/5/17
+ */
+class Boundary {
+
+	private double northLat, eastLng, southLat, westLng;
+
+	Boundary(double northLat, double eastLng, double southLat, double westLng) {
+		this.northLat = northLat;
+		this.eastLng = eastLng;
+		this.southLat = southLat;
+		this.westLng = westLng;
+	}
+
+	double getCentreLat() {
+		return (northLat + southLat) / 2;
+	}
+
+	double getCentreLng() {
+		return (eastLng + westLng) / 2;
+	}
+
+	double getNorthLat() {
+		return northLat;
+	}
+
+	double getEastLng() {
+		return eastLng;
+	}
+
+	double getSouthLat() {
+		return southLat;
+	}
+
+	double getWestLng() {
+		return westLng;
+	}
+}

src/main/java/seng302/visualiser/map/CanvasMap.java

@@ -0,0 +1,103 @@
+package seng302.visualiser.map;
+
+import java.net.URL;
+import javafx.geometry.Point2D;
+import javafx.scene.image.Image;
+import javax.net.ssl.HttpsURLConnection;
+import seng302.utilities.GeoPoint;
+
+/**
+ * CanvasMap retrieves a map image with given geo boundary from Google Map server.
+ * By passing a rectangle like geo boundary, it returns a map image with the
+ * highest resolution. However, due to free quote account usage limit, the maximum
+ * resolution is only 1280 * 1280.
+ *
+ * Created by Haoming on 15/5/2017
+ */
+public class CanvasMap {
+
+	private Boundary boundary;
+	private long width, height;  // desired image size
+	private int zoom;
+
+	private String KEY = "AIzaSyC-5oOShMCY5Oy_9L7guYMPUPFHDMr37wE";
+
+	CanvasMap(Boundary boundary) {
+		this.boundary = boundary;
+		calculateOptimalMapSize();
+	}
+
+	Image getMapImage() {
+		try {
+			URL url = new URL(getRequest());
+			HttpsURLConnection connection = (HttpsURLConnection) url.openConnection();
+
+			return new Image(connection.getInputStream());
+		} catch (Exception e) {
+			System.out.println("[CanvasMap] Exception");
+			return null;
+		}
+	}
+
+	private String getRequest() {
+		StringBuilder sb = new StringBuilder();
+		sb.append("https://maps.googleapis.com/maps/api/staticmap?");
+		sb.append(String.format("center=%f,%f", boundary.getCentreLat(), boundary.getCentreLng()));
+		sb.append(String.format("&zoom=%d", zoom));
+		sb.append(String.format("&size=%dx%d&scale=2", width, height));
+		sb.append("&style=feature:all|element:labels|visibility:off"); // hide all labels on map
+//		sb.append(String.format("&markers=%f,%f", boundary.getSouthLat(), boundary.getWestLng()));
+//		sb.append(String.format("&key=%s", KEY));
+		return sb.toString();
+	}
+
+	private void calculateOptimalMapSize() {
+		for (int z = 20; z > 0; z--) {
+			MapSize mapSize = getMapSize(z, boundary);
+			zoom = z;
+			width = mapSize.width;
+			height = mapSize.height;
+			// if map size is valid, exit the loop as we have the highest resolution
+			if (mapSize.isValid()) break;
+		}
+	}
+
+	private MapSize getMapSize(int zoom, Boundary boundary) {
+		double scale = Math.pow(2, zoom);
+		GeoPoint geoSW = new GeoPoint(boundary.getSouthLat(), boundary.getWestLng());
+		GeoPoint geoNE = new GeoPoint(boundary.getNorthLat(), boundary.getEastLng());
+		Point2D pointSW = MercatorProjection.toMapPoint(geoSW);
+		Point2D pointNE = MercatorProjection.toMapPoint(geoNE);
+		return new MapSize(Math.abs(pointNE.getX() - pointSW.getX()) * scale,
+				Math.abs(pointNE.getY() - pointSW.getY()) * scale);
+	}
+
+	class MapSize {
+		long width, height;
+
+		MapSize(double width, double height) {
+			this.width = Math.round(width);
+			this.height = Math.round(height);
+		}
+
+		/**
+		 * Map size is valid when width and height are both less than 640 pixels
+		 * @return true if both dimensions are less than 640px
+		 */
+		boolean isValid() {
+			return Math.max(width, height) <= 640;
+		}
+	}
+
+	public long getWidth() {
+		return width;
+	}
+
+	public long getHeight() {
+		return height;
+	}
+
+	public int getZoom() {
+		return zoom;
+	}
+}

src/main/java/seng302/visualiser/map/MercatorProjection.java

@@ -0,0 +1,55 @@
+package seng302.visualiser.map;
+
+import javafx.geometry.Point2D;
+import seng302.utilities.GeoPoint;
+
+/**
+ * An utility class useful to convert between Geo locations and Mercator projection
+ * planar coordinates.
+ * Created by Haoming on 15/5/2017
+ */
+public class MercatorProjection {
+
+	private static final double MERCATOR_RANGE = 256;
+	private static final double pixelsPerLngDegree = MERCATOR_RANGE / 360.0;
+	private static final double pixelsPerLngRadian = MERCATOR_RANGE / (2 * Math.PI);
+
+	/**
+	 * A help function keeps the value in bound between -0.9999 and 0.9999.
+	 * @param value in bound value
+	 * @return the value in bound
+	 */
+	private static double bound(double value) {
+		return Math.min(Math.max(value, -0.9999), 0.9999);
+	}
+
+	/**
+	 * Projects a Geo Location (lat, lng) on a planar
+	 * @param geo GeoPoint (lat, lng) location to be projected
+	 * @return the projection Point2D (x, y) on planar
+	 */
+	static Point2D toMapPoint(GeoPoint geo) {
+		double x, y;
+		Point2D origin = new Point2D(MERCATOR_RANGE / 2.0, MERCATOR_RANGE / 2.0);
+		x = (origin.getX() + geo.getLng() * pixelsPerLngDegree);
+
+//		NOTE(appleton): Truncating to 0.9999 effectively limits latitude to
+//      89.189.  This is about a third of a tile past the edge of the world tile.
+		double sinY = bound(Math.sin(Math.toRadians(geo.getLat())));
+		y = origin.getY() + 0.5 * Math.log((1 + sinY) / (1 - sinY)) * (-pixelsPerLngRadian);
+		return new Point2D(x, y);
+	}
+
+	/**
+	 * Converts the planar projection (x, y) back to Geo Location (lat, lng)
+	 * @param point Point2D (x, y) to be converted back
+	 * @return the original Geo location converted from the given projection point
+	 */
+	public static GeoPoint toMapGeo(Point2D point) {
+		Point2D origin = new Point2D(MERCATOR_RANGE / 2.0, MERCATOR_RANGE / 2.0);
+		double lng = (point.getX() - origin.getX()) / pixelsPerLngDegree;
+		double latRadians = (point.getY() - origin.getY()) / (-pixelsPerLngRadian);
+		double lat = Math.toDegrees(2 * Math.atan(Math.exp(latRadians)) - Math.PI / 2.0);
+		return new GeoPoint(lat, lng);
+	}
+}

src/main/java/seng302/visualiser/map/TestMapController.java

@@ -0,0 +1,22 @@
+package seng302.visualiser.map;
+
+import java.net.URL;
+import java.util.ResourceBundle;
+import javafx.fxml.FXML;
+import javafx.fxml.Initializable;
+import javafx.scene.canvas.Canvas;
+import javafx.scene.canvas.GraphicsContext;
+
+public class TestMapController implements Initializable{
+
+	@FXML
+	private Canvas mapCanvas;
+
+	@Override
+	public void initialize(URL location, ResourceBundle resources) {
+		GraphicsContext gc = mapCanvas.getGraphicsContext2D();
+		Boundary bound = new Boundary(57.662943, 11.848501, 57.673945, 11.824966);
+		CanvasMap canvasMap = new CanvasMap(bound);
+		gc.drawImage(canvasMap.getMapImage(), 0, 0, canvasMap.getWidth(), canvasMap.getHeight());
+	}
+}