path: root/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/Projection.java

package com.mapbox.mapboxsdk.maps;

import android.graphics.PointF;
import android.support.annotation.FloatRange;
import android.support.annotation.NonNull;

import com.mapbox.geojson.Point;
import com.mapbox.mapboxsdk.constants.GeometryConstants;
import com.mapbox.mapboxsdk.geometry.LatLng;
import com.mapbox.mapboxsdk.geometry.LatLngBounds;
import com.mapbox.mapboxsdk.geometry.ProjectedMeters;
import com.mapbox.mapboxsdk.geometry.VisibleRegion;

import java.util.ArrayList;
import java.util.List;

/**
 * A projection is used to translate between on screen location and geographic coordinates on
 * the surface of the Earth. Screen location is in screen pixels (not display pixels)
 * with respect to the top left corner of the map (and not necessarily of the whole screen).
 */
public class Projection {

  @NonNull
  private final NativeMap nativeMapView;
  @NonNull
  private final MapView mapView;

  Projection(@NonNull NativeMap nativeMapView, @NonNull MapView mapView) {
    this.nativeMapView = nativeMapView;
    this.mapView = mapView;
  }

  void setContentPadding(int[] contentPadding) {
    double[] output = new double[contentPadding.length];
    for (int i = 0; i < contentPadding.length; i++) {
      output[i] = contentPadding[i];
    }
    nativeMapView.setContentPadding(output);
  }

  int[] getContentPadding() {
    double[] padding = nativeMapView.getCameraPosition().padding;
    return new int[] {(int) padding[0], (int) padding[1], (int) padding[2], (int) padding[3]};
  }

  /**
   * @deprecated unused
   */
  @Deprecated
  public void invalidateContentPadding() {
  }

  /**
   * Returns the spherical Mercator projected meters for a LatLng.
   */
  @NonNull
  public ProjectedMeters getProjectedMetersForLatLng(@NonNull LatLng latLng) {
    return nativeMapView.projectedMetersForLatLng(latLng);
  }

  /**
   * Returns the LatLng for a spherical Mercator projected meters.
   */
  @NonNull
  public LatLng getLatLngForProjectedMeters(@NonNull ProjectedMeters projectedMeters) {
    return nativeMapView.latLngForProjectedMeters(projectedMeters);
  }

  /**
   * <p>
   * Returns the distance spanned by one pixel at the specified latitude and current zoom level.
   * </p>
   * The distance between pixels decreases as the latitude approaches the poles.
   * This relationship parallels the relationship between longitudinal coordinates at different latitudes.
   *
   * @param latitude The latitude for which to return the value.
   * @return The distance measured in meters.
   */
  public double getMetersPerPixelAtLatitude(@FloatRange(from = -90, to = 90) double latitude) {
    return nativeMapView.getMetersPerPixelAtLatitude(latitude);
  }

  /**
   * Returns the geographic location that corresponds to a screen location.
   * The screen location is specified in screen pixels (not display pixels) relative to the
   * top left of the map (not the top left of the whole screen).
   *
   * @param point A Point on the screen in screen pixels.
   * @return The LatLng corresponding to the point on the screen, or null if the ray through
   * the given screen point does not intersect the ground plane.
   */
  @NonNull
  public LatLng fromScreenLocation(@NonNull PointF point) {
    return nativeMapView.latLngForPixel(point);
  }

  /**
   * Gets a projection of the viewing frustum for converting between screen coordinates and
   * geo-latitude/longitude coordinates.
   * <p>
   * This method ignores the content padding.
   *
   * @return The projection of the viewing frustum in its current state.
   */
  @NonNull
  public VisibleRegion getVisibleRegion() {
    return getVisibleRegion(true);
  }

  /**
   * Gets a projection of the viewing frustum for converting between screen coordinates and
   * geo-latitude/longitude coordinates.
   *
   * @param ignorePadding True if the padding should be ignored,
   *                      false if the returned region should be reduced by the padding.
   * @return The projection of the viewing frustum in its current state.
   */
  @NonNull
  public VisibleRegion getVisibleRegion(boolean ignorePadding) {
    float left;
    float right;
    float top;
    float bottom;

    if (ignorePadding) {
      left = 0;
      right = mapView.getWidth();
      top = 0;
      bottom = mapView.getHeight();
    } else {
      int[] contentPadding = getContentPadding();
      left = contentPadding[0];
      right = mapView.getWidth() - contentPadding[2];
      top = contentPadding[1];
      bottom = mapView.getHeight() - contentPadding[3];
    }

    LatLng center = fromScreenLocation(new PointF(left + (right - left) / 2, top + (bottom - top) / 2));

    LatLng topLeft = fromScreenLocation(new PointF(left, top));
    LatLng topRight = fromScreenLocation(new PointF(right, top));
    LatLng bottomRight = fromScreenLocation(new PointF(right, bottom));
    LatLng bottomLeft = fromScreenLocation(new PointF(left, bottom));

    List<LatLng> latLngs = new ArrayList<>();
    latLngs.add(topRight);
    latLngs.add(bottomRight);
    latLngs.add(bottomLeft);
    latLngs.add(topLeft);

    double maxEastLonSpan = 0;
    double maxWestLonSpan = 0;

    double east = 0;
    double west = 0;
    double north = GeometryConstants.MIN_LATITUDE;
    double south = GeometryConstants.MAX_LATITUDE;

    for (LatLng latLng : latLngs) {
      double bearing = bearing(center, latLng);

      if (bearing >= 0) {
        double span = getLongitudeSpan(latLng.getLongitude(), center.getLongitude());
        if (span > maxEastLonSpan) {
          maxEastLonSpan = span;
          east = latLng.getLongitude();
        }
      } else {
        double span = getLongitudeSpan(center.getLongitude(), latLng.getLongitude());
        if (span > maxWestLonSpan) {
          maxWestLonSpan = span;
          west = latLng.getLongitude();
        }
      }

      if (north < latLng.getLatitude()) {
        north = latLng.getLatitude();
      }
      if (south > latLng.getLatitude()) {
        south = latLng.getLatitude();
      }
    }

    if (east < west) {
      return new VisibleRegion(topLeft, topRight, bottomLeft, bottomRight,
        LatLngBounds.from(north, east + GeometryConstants.LONGITUDE_SPAN, south, west));
    }
    return new VisibleRegion(topLeft, topRight, bottomLeft, bottomRight,
      LatLngBounds.from(north, east, south, west));
  }

  /**
   * Takes two {@link Point}s and finds the geographic bearing between them.
   *
   * @param latLng1 the first point used for calculating the bearing
   * @param latLng2 the second point used for calculating the bearing
   * @return bearing in decimal degrees
   * @see <a href="http://turfjs.org/docs/#bearing">Turf Bearing documentation</a>
   */
  static double bearing(@NonNull LatLng latLng1, @NonNull LatLng latLng2) {

    double lon1 = degreesToRadians(latLng1.getLongitude());
    double lon2 = degreesToRadians(latLng2.getLongitude());
    double lat1 = degreesToRadians(latLng1.getLatitude());
    double lat2 = degreesToRadians(latLng2.getLatitude());

    double value1 = Math.sin(lon2 - lon1) * Math.cos(lat2);
    double value2 = Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1)
      * Math.cos(lat2) * Math.cos(lon2 - lon1);

    return radiansToDegrees(Math.atan2(value1, value2));
  }

  /**
   * Converts an angle in degrees to radians.
   *
   * @param degrees angle between 0 and 360 degrees
   * @return angle in radians
   */
  static double degreesToRadians(double degrees) {
    double radians = degrees % 360;
    return radians * Math.PI / 180;
  }

  /**
   * Converts an angle in radians to degrees.
   *
   * @param radians angle in radians
   * @return degrees between 0 and 360 degrees
   */
  static double radiansToDegrees(double radians) {
    double degrees = radians % (2 * Math.PI);
    return degrees * 180 / Math.PI;
  }

  /**
   * Get the absolute distance, in degrees, between the west and
   * east boundaries of this LatLngBounds
   *
   * @return Span distance
   */
  static double getLongitudeSpan(double east, double west) {
    double longSpan = Math.abs(east - west);
    if (east > west) {
      return longSpan;
    }

    // shortest span contains antimeridian
    return GeometryConstants.LONGITUDE_SPAN - longSpan;
  }

  /**
   * Returns a screen location that corresponds to a geographical coordinate (LatLng).
   * The screen location is in screen pixels (not display pixels) relative to the top left
   * of the map (not of the whole screen).
   *
   * @param location A LatLng on the map to convert to a screen location.
   * @return A Point representing the screen location in screen pixels.
   */
  @NonNull
  public PointF toScreenLocation(@NonNull LatLng location) {
    return nativeMapView.pixelForLatLng(location);
  }

  float getHeight() {
    return mapView.getHeight();
  }

  float getWidth() {
    return mapView.getWidth();
  }

  /**
   * Calculates a zoom level based on minimum scale and current scale from MapView
   *
   * @param minScale The minimum scale to calculate the zoom level.
   * @return zoom level that fits the MapView.
   */
  public double calculateZoom(float minScale) {
    return nativeMapView.getZoom() + Math.log(minScale) / Math.log(2);
  }
}