Added methods to calculate optimal map size given a geo boundary.

- From zoom level 20 to 1, once find a size that contains the whole boundary, then the size will be used to retrieve map image from google

#story[928]

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

@@ -7,18 +7,25 @@ import java.net.URL;
 
 import java.lang.Math;
 
+/**
+ * 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 bound;
-	private double width, height;  // desired image size
+	private Boundary boundary;
+	private long width, height;  // desired image size
 	private int zoom;
 
 	private String KEY = "AIzaSyC-5oOShMCY5Oy_9L7guYMPUPFHDMr37wE";
 
-	public CanvasMap(Boundary bound, double width, double height) {
-		this.bound = bound;
-		this.width = width;
-		this.height = height;
+	public CanvasMap(Boundary boundary) {
+		this.boundary = boundary;
+		calculateOptimalMapSize();
 	}
 
 	public Image getMapImage() {
@@ -35,33 +42,64 @@ public class CanvasMap {
 	}
 
 	private String getRequest() {
-		zoom = 15;
 		StringBuilder sb = new StringBuilder();
 		sb.append("https://maps.googleapis.com/maps/api/staticmap?");
-		sb.append(String.format("center=%f,%f", bound.getCentreLat(), bound.getCentreLng()));
+		sb.append(String.format("center=%f,%f", boundary.getCentreLat(), boundary.getCentreLng()));
 		sb.append(String.format("&zoom=%d", zoom));
-		sb.append(String.format("&size=%.0fx%.0f&scale=2", width / 2, height / 2));
+		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);
 		MapGeo geoSW = new MapGeo(boundary.getSouthLat(), boundary.getWestLng());
 		MapGeo geoNE = new MapGeo(boundary.getNorthLat(), boundary.getEastLng());
 		MapPoint pointSW = MercatorProjection.toMapPoint(geoSW);
 		MapPoint pointNE = MercatorProjection.toMapPoint(geoNE);
-		return new MapSize(Math.abs(pointNE.getX() - pointSW.getX()),
-				Math.abs(pointNE.getY() - pointSW.getY()));
+		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 = (long) width;
-			this.height = (long) 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;
+	}
 }