Pan&Zoom是个很常用的操作，但是不想每次都去重新写各种GerstureListener事件，所以就参考这篇，改写了个简单的Behavior。

public class ZoomAndPanBehavior2 : Behavior<Image>

{

private Image _currentImage { get { return AssociatedObject as Image; } }

 

private PhoneApplicationPage _currentPage

{

get

{

var rootFrame = Application.Current.RootVisual as PhoneApplicationFrame;

var currentPage = rootFrame.Content as PhoneApplicationPage;

return currentPage;

}

}

 

private GestureListener _gl { get { return GestureService.GetGestureListener(_currentImage); } }

 

private double _totalImageScale = 1d;

private Point _imagePosition = new Point(0, 0);

 

private Point _oldFinger1;

private Point _oldFinger2;

private double _oldScaleFactor; //旧的缩放因子

 

private CompositeTransform _compositeTransfrom;

private MatrixTransform _previousTransform;

private TransformGroup _transfromGruop;

private TransformGroup _currentGroup;

 

bool isDragging;

bool isPinching;

Point ptPinchPositionStart;

 

protected override void OnAttached()

{

base.OnAttached();

_compositeTransfrom = new CompositeTransform();

_previousTransform = new MatrixTransform { Matrix = Matrix.Identity };

_transfromGruop = new TransformGroup();

_currentGroup = new TransformGroup();

_currentGroup.Children.Add(_compositeTransfrom);

_transfromGruop.Children.Add(_currentGroup);

_transfromGruop.Children.Add(_previousTransform);

_currentImage.RenderTransform = _transfromGruop;

_currentImage.RenderTransformOrigin = new Point(0, 0);

_gl.DragStarted += _gl_DragStarted;

_gl.DragDelta += _gl_DragDelta;

_gl.PinchStarted += _gl_PinchStarted;

_gl.PinchDelta += _gl_PinchDelta;

_gl.PinchCompleted += _gl_PinchCompleted;

_gl.Hold += _gl_Hold;

_gl.DoubleTap += _gl_DoubleTap;

}

 

protected override void OnDetaching()

{

base.OnDetaching();

_gl.DragStarted -= _gl_DragStarted;

_gl.DragDelta -= _gl_DragDelta;

_gl.PinchStarted -= _gl_PinchStarted;

_gl.PinchDelta -= _gl_PinchDelta;

_gl.PinchCompleted -= _gl_PinchCompleted;

_gl.Hold -= _gl_Hold;

_gl.DoubleTap -= _gl_DoubleTap;

_compositeTransfrom = null;

}

 

void _gl_DoubleTap(object sender, Microsoft.Phone.Controls.GestureEventArgs e)

{

Point imageCenter = e.GetPosition(_currentImage);

if (_compositeTransfrom.ScaleX != 2)

_compositeTransfrom.ScaleY = _compositeTransfrom.ScaleX = 2;

else

_compositeTransfrom.ScaleX = _compositeTransfrom.ScaleY = 1;

_compositeTransfrom.CenterX = imageCenter.X;

_compositeTransfrom.CenterY = imageCenter.Y;

}

 

void _gl_Hold(object sender, Microsoft.Phone.Controls.GestureEventArgs e)

{

 

}

 

void _gl_PinchStarted(object sender, PinchStartedGestureEventArgs e)

{

_oldFinger1 = e.GetPosition(_currentImage, 0);

_oldFinger2 = e.GetPosition(_currentImage, 1);

_oldScaleFactor = 1;

isPinching = true;

}

void _gl_PinchDelta(object sender, PinchGestureEventArgs e)

{

//DistanceRatio表示缩放之后手指之间的距离与缩放前手指之间距离的比例

var scaleFactor = e.DistanceRatio / _oldScaleFactor;

 

var currentFinger1 = e.GetPosition(_currentImage, 0);

var currentFinger2 = e.GetPosition(_currentImage, 1);

 

Point tranlationDelta;

tranlationDelta = GetTranslationDelta(currentFinger1, currentFinger2, _oldFinger1, _oldFinger2, _imagePosition, scaleFactor);

 

_oldFinger1 = currentFinger1;

_oldFinger2 = currentFinger2;

_oldScaleFactor = e.DistanceRatio;

UpdateImage(scaleFactor, tranlationDelta);

}

 

void _gl_PinchCompleted(object sender, PinchGestureEventArgs e)

{

isPinching = false;

}

 

void _gl_DragStarted(object sender, DragStartedGestureEventArgs e)

{

 

}

 

void _gl_DragDelta(object sender, DragDeltaGestureEventArgs e)

{

if (isPinching)

return;

if (_totalImageScale > 1 || _compositeTransfrom.ScaleX > 1)

{

_compositeTransfrom.TranslateX += e.HorizontalChange;

_compositeTransfrom.TranslateY += e.VerticalChange;

}

}

 

private void UpdateImage(double scaleFactor, Point delta)

{

_totalImageScale *= scaleFactor;

_imagePosition = new Point(_imagePosition.X + delta.X, _imagePosition.Y + delta.Y);

 

if (_totalImageScale > 1)

{

_compositeTransfrom.ScaleX = _totalImageScale;

_compositeTransfrom.ScaleY = _totalImageScale;

_compositeTransfrom.TranslateX = _imagePosition.X;

_compositeTransfrom.TranslateY = _imagePosition.Y;

}

else

{

_compositeTransfrom.ScaleX = _compositeTransfrom.ScaleY = 1;

_compositeTransfrom.TranslateX = _compositeTransfrom.TranslateY = 0;

_imagePosition = new Point(0, 0);

}

}

 

private Point GetTranslationDelta(Point currentFinger1, Point currentFinger2, Point oldFinger1,

Point oldFinger2, Point currentPosition, double scaleFactor)

{

var newPos1 = new Point(

currentFinger1.X + (currentPosition.X - oldFinger1.X) * scaleFactor,

currentFinger1.Y + (currentPosition.Y - oldFinger1.Y) * scaleFactor);

 

var newPos2 = new Point(

currentFinger2.X + (currentPosition.X - oldFinger2.X) * scaleFactor,

currentFinger2.Y + (currentPosition.Y - oldFinger2.Y) * scaleFactor);

 

var newPos = new Point(

(newPos1.X + newPos2.X) / 2,

(newPos1.Y + newPos2.Y) / 2);

 

return new Point(

newPos.X - currentPosition.X,

newPos.Y - currentPosition.Y);

}

}