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. 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 final MapView mapView; private final float screenDensity; private final PointF screenLocationPoint; Projection(@NonNull MapView mapView) { this.mapView = mapView; this.screenLocationPoint = new PointF(); this.screenDensity = mapView.getContext() != null ? /* return default if unit test */ mapView.getContext().getResources().getDisplayMetrics().density : 1.0f; } /** *
* Returns the distance spanned by one pixel at the specified latitude and current zoom level. *
* 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 mapView.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) { screenLocationPoint.set(point.x / screenDensity, point.y / screenDensity); return mapView.fromNativeScreenLocation(screenLocationPoint); } /** * 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(); float left = mapView.getContentPaddingLeft(); float right = mapView.getWidth() - mapView.getContentPaddingRight(); float top = mapView.getContentPaddingTop(); float bottom = mapView.getHeight() - mapView.getContentPaddingBottom(); 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)); 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) { PointF pointF = mapView.toNativeScreenLocation(location); pointF.set(pointF.x * screenDensity, pointF.y * screenDensity); return pointF; } /** * 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(mapView.getScale() * minScale) / Math.log(2); } }