Camera with Pan and Zoom

Camera.cs

using Microsoft.Xna.Framework;
using ZoomEngine.Animation;

namespace Game
{
   public class Camera
   {
      private ClockManager _clockManager;

      // position of the camera
      public Camera( int viewportWidth, int viewportHeight, Vector2 cameraPosition, ClockManager clockManager )
      {
         ViewportWidth = viewportWidth;
         ViewportHeight = viewportHeight;
         Position = cameraPosition;
         _clockManager = clockManager;
         Zoom = 1.0f;
      }

      // Centered Position of the Camera.
      public Vector2 Position { get; private set; }
      public float Zoom { get; private set; }
      public float Rotation { get; private set; }

      // height and width of the viewport window which should adjust when the player resizes the game window.
      public int ViewportWidth { get; set; }
      public int ViewportHeight { get; set; }

      // Center of the Viewport does not account for scale
      public Vector2 ViewportCenter
      {
         get
         {
            return new Vector2( ViewportWidth * 0.5f, ViewportHeight * 0.5f );
         }
      }

      // create a matrix for the camera to offset everything we draw, the map and our objects. since the
      // camera coordinates are where the camera is, we offset everything by the negative of that to simulate
      // a camera moving. we also cast to integers to avoid filtering artifacts
      public Matrix TranslationMatrix
      {
         get
         {
            return Matrix.CreateTranslation( -(int) Position.X, -(int) Position.Y, 0 ) *
               Matrix.CreateRotationZ( Rotation ) *
               Matrix.CreateScale( new Vector3( Zoom, Zoom, 1 ) ) *
               Matrix.CreateTranslation( new Vector3( ViewportCenter, 0 ) );
         }
      }

      public void AdjustZoom( float amount )
      {
         Zoom += amount;
         if ( Zoom < 0.1f )
         {
            Zoom = 0.1f;
         }
      }

      public void MoveCamera( Vector2 cameraMovement, bool clampToMap = false )
      {
         Position += cameraMovement;

         if ( clampToMap )
         {
            // clamp the camera so it never leaves the visible area of the map.
            var cameraMax = new Vector2( Global.GameModel.Map.Width * Global.CellWidth - ViewportWidth,
                                         Global.GameModel.Map.Height * Global.CellHeight - ViewportHeight );

            Position = Vector2.Clamp( Position, Vector2.Zero, cameraMax );
         }
      }

      public void Shake( double duration )
      {
         StateManager.StartAnimation();

         var positionAnim = new Vector2FromToAnimation( _clockManager )
         {
            From = new Vector2( Position.X + 1, Position.Y + 1 ),
            To = Position,
            Duration = duration,
            ProgressTransform = ProgressTransforms.Elastic( 3, 10 ),
            Apply = f => Position = f
         };

         positionAnim.Complete += ( s, e ) =>
         {
            StateManager.StopAnimation();
         };

         positionAnim.Start();
      }

      public void PanTo( Point location )
      {
         Vector2 originalPosition = Position;
         Vector2 targetPosition = CenteredPosition( location );
         if ( originalPosition.Equals( targetPosition ) )
         {
            return;
         }
         StateManager.StartAnimation();
         float distanceBetween;
         Vector2.Distance( ref originalPosition, ref targetPosition, out distanceBetween );
         distanceBetween = ( distanceBetween / Global.CellHeight );
         double duration = MathHelper.Clamp( .05f * distanceBetween, .05f, .3f );

         var positionAnim = new Vector2FromToAnimation( _clockManager )
         {
            From = originalPosition,
            To = targetPosition,
            Duration = duration,
            ProgressTransform = ProgressTransforms.Snake( 1 ),
            Apply = f => Position = f
         };

         positionAnim.Complete += ( s, e ) =>
         {
            StateManager.StopAnimation();
         };

         positionAnim.Start();
      }

      public Rectangle ViewportWorldBoundry()
      {
         Vector2 viewPortCorner = ScreenToWorld( new Vector2( 0, 0 ) );
         Vector2 viewPortBottomCorner = ScreenToWorld( new Vector2( ViewportWidth, ViewportHeight ) );

         return new Rectangle( (int) viewPortCorner.X, (int) viewPortCorner.Y, (int) ( viewPortBottomCorner.X - viewPortCorner.X ),
                                                (int) ( viewPortBottomCorner.Y - viewPortCorner.Y ) );
      }

      public void CenterOn( Vector2 position )
      {
         Position = position;
      }

      public void CenterOn( Point location )
      {
         Position = CenteredPosition( location );
      }

      private Vector2 CenteredPosition( Point location, bool clampToMap = false )
      {
         var cameraPosition = new Vector2( location.X * Global.CellWidth, location.Y * Global.CellHeight );
         var cameraCenteredOnTilePosition = new Vector2( cameraPosition.X + Global.HalfCellWidth,
                                                         cameraPosition.Y + Global.HalfCellHeight );
         if ( clampToMap )
         {
            // clamp the camera so it never leaves the visible area of the map.
            var cameraMax = new Vector2( Global.GameModel.Map.Width * Global.CellWidth - ViewportWidth,
                                         Global.GameModel.Map.Height * Global.CellHeight - ViewportHeight );

            return Vector2.Clamp( cameraCenteredOnTilePosition, Vector2.Zero, cameraMax );
         }

         return cameraCenteredOnTilePosition;
      }

      public Vector2 WorldToScreen( Vector2 worldPosition )
      {
         return Vector2.Transform( worldPosition, TranslationMatrix );
      }

      public Vector2 ScreenToWorld( Vector2 screenPosition )
      {
         return Vector2.Transform( screenPosition, Matrix.Invert( TranslationMatrix ) );
      }

      public void HandleInput( InputState inputState, PlayerIndex? controllingPlayer )
      {
         // Move the camera's position based on WASD or Right thumbstick input
         Vector2 cameraMovement = Vector2.Zero;

         if ( inputState.IsScrollLeft( controllingPlayer ) )
         {
            cameraMovement.X = -1;
         }
         else if ( inputState.IsScrollRight( controllingPlayer ) )
         {
            cameraMovement.X = 1;
         }
         if ( inputState.IsScrollUp( controllingPlayer ) )
         {
            cameraMovement.Y = -1;
         }
         else if ( inputState.IsScrollDown( controllingPlayer ) )
         {
            cameraMovement.Y = 1;
         }

         // to match the thumbstick behavior, we need to normalize non-zero vectors in case the user
         // is pressing a diagonal direction.
         if ( cameraMovement != Vector2.Zero )
         {
            cameraMovement.Normalize();
         }

         // scale our movement to move 25 pixels per second
         cameraMovement *= 25f;

         // move the camera
         MoveCamera( cameraMovement );
      }
   }
}