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package com.mapbox.mapboxsdk.maps;
import android.graphics.PointF;
import android.support.annotation.FloatRange;
import android.support.annotation.NonNull;
import com.mapbox.mapboxsdk.geometry.LatLng;
import com.mapbox.mapboxsdk.geometry.LatLngBounds;
import com.mapbox.mapboxsdk.geometry.VisibleRegion;
/**
* A projection is used to translate between on screen location and geographic coordinates on
* the surface of the Earth (LatLng). 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 {
private MapView mMapView;
Projection(@NonNull MapView mapView) {
this.mMapView = mapView;
}
/**
* <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 = -180, to = 180) double latitude) {
return mMapView.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.
*/
public LatLng fromScreenLocation(PointF point) {
return mMapView.fromScreenLocation(point);
}
/**
* Gets a projection of the viewing frustum for converting between screen coordinates and
* geo-latitude/longitude coordinates.
*
* @return The projection of the viewing frustum in its current state.
*/
public VisibleRegion getVisibleRegion() {
LatLngBounds.Builder builder = new LatLngBounds.Builder();
int viewportWidth = mMapView.getWidth();
int viewportHeight = mMapView.getHeight();
LatLng topLeft = fromScreenLocation(new PointF(0, 0));
LatLng topRight = fromScreenLocation(new PointF(viewportWidth, 0));
LatLng bottomRight = fromScreenLocation(new PointF(viewportWidth, viewportHeight));
LatLng bottomLeft = fromScreenLocation(new PointF(0, viewportHeight));
builder.include(topLeft)
.include(topRight)
.include(bottomRight)
.include(bottomLeft);
return new VisibleRegion(topLeft, topRight, bottomLeft, bottomRight, builder.build());
}
/**
* 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.
*/
public PointF toScreenLocation(LatLng location) {
return mMapView.toScreenLocation(location);
}
/**
* 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 Math.log(mMapView.getScale() * minScale) / Math.log(2);
}
}
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