mnbayan · February 23, 2015 02:33 · Feb 23, 2015
diff --git a/MKMapViewExtension.swift b/MKMapViewExtension.swift
@@ -0,0 +1,82 @@
+//
+//  MKMapViewExtension.swift
+//  AutocompleteTextfieldSwift
+//
+//  Created by Mylene Bayan on 2/22/15.
+//  Copyright (c) 2015 MaiLin. All rights reserved.
+//
+
+import Foundation
+import MapKit
+
+
+let MERCATOR_OFFSET = 268435456.0
+let MERCATOR_RADIUS = 85445659.44705395
+let DEGREES = 180.0
+
+extension MKMapView{
+  //MARK: Map Conversion Methods
+  private func longitudeToPixelSpaceX(longitude:Double)->Double{
+    return round(MERCATOR_OFFSET + MERCATOR_RADIUS * longitude * M_PI / DEGREES)
+  }
+
+  private func latitudeToPixelSpaceY(latitude:Double)->Double{
+    return round(MERCATOR_OFFSET - MERCATOR_RADIUS * log((1 + sin(latitude * M_PI / DEGREES)) / (1 - sin(latitude * M_PI / DEGREES))) / 2.0)
+  }
+
+  private func pixelSpaceXToLongitude(pixelX:Double)->Double{
+    return ((round(pixelX) - MERCATOR_OFFSET) / MERCATOR_RADIUS) * DEGREES / M_PI
+
+  }
+
+  private func pixelSpaceYToLatitude(pixelY:Double)->Double{
+    return (M_PI / 2.0 - 2.0 * atan(exp((round(pixelY) - MERCATOR_OFFSET) / MERCATOR_RADIUS))) * DEGREES / M_PI
+  }
+
+  private func coordinateSpanWithCenterCoordinate(centerCoordinate:CLLocationCoordinate2D, zoomLevel:Double)->MKCoordinateSpan{
+
+    // convert center coordiate to pixel space
+    let centerPixelX = longitudeToPixelSpaceX(centerCoordinate.longitude)
+    let centerPixelY = latitudeToPixelSpaceY(centerCoordinate.latitude)
+
+    // determine the scale value from the zoom level
+    let zoomExponent:Double = 20.0 - zoomLevel
+    let zoomScale:Double = pow(2.0, zoomExponent)
+
+    // scale the map’s size in pixel space
+    let mapSizeInPixels = self.bounds.size
+    let scaledMapWidth = Double(mapSizeInPixels.width) * zoomScale
+    let scaledMapHeight = Double(mapSizeInPixels.height) * zoomScale
+
+    // figure out the position of the top-left pixel
+    let topLeftPixelX = centerPixelX - (scaledMapWidth / 2.0)
+    let topLeftPixelY = centerPixelY - (scaledMapHeight / 2.0)
+
+    // find delta between left and right longitudes
+    let minLng = pixelSpaceXToLongitude(topLeftPixelX)
+    let maxLng = pixelSpaceXToLongitude(topLeftPixelX + scaledMapWidth)
+    let longitudeDelta = maxLng - minLng
+
+    let minLat = pixelSpaceYToLatitude(topLeftPixelY)
+    let maxLat = pixelSpaceYToLatitude(topLeftPixelY + scaledMapHeight)
+    let latitudeDelta = -1.0 * (maxLat - minLat)
+
+    return MKCoordinateSpan(latitudeDelta: latitudeDelta, longitudeDelta: longitudeDelta)
+  }
+
+  func setCenterCoordinate(centerCoordinate:CLLocationCoordinate2D, var zoomLevel:Double, animated:Bool){
+    // clamp large numbers to 28
+    zoomLevel = min(zoomLevel, 28)
+
+      // use the zoom level to compute the region
+    let span = self.coordinateSpanWithCenterCoordinate(centerCoordinate, zoomLevel: zoomLevel)
+    let region = MKCoordinateRegionMake(centerCoordinate, span)
+    if region.center.longitude == -180.00000000{
+      println("Invalid Region")
+    }
+    else{
+      self.setRegion(region, animated: animated)
+    }
+  }
+
+}