WPF关于图片定点缩放的问题

[weixin_38061090]

最近做图片定点缩放遇到点问题，需要同时支持pc和触摸系统，看了网上很多例子，PC上可以用
<Grid x:Name="MainPanel" >
            <Grid.Resources>
                <TransformGroup x:Key="ImageTransformResource">
                    <ScaleTransform />
                    <TranslateTransform />
                </TransformGroup>
            </Grid.Resources>

            <Rectangle x:Name="MasterImage"
                MouseLeftButtonDown="MasterImage_MouseLeftButtonDown"
                MouseLeftButtonUp="MasterImage_MouseLeftButtonUp"
                MouseMove="MasterImage_MouseMove"
                MouseWheel="MasterImage_MouseWheel"
                ManipulationStarting="TouchPad_ManipulationStarting"
                ManipulationDelta="TouchPad_ManipulationDelta"
                       IsManipulationEnabled="True">
                <Rectangle.Fill>
                    <VisualBrush Transform="{StaticResource ImageTransformResource}" Stretch="Uniform">
                        <VisualBrush.Visual>
                            <Image Name="imgToDisplay"></Image>
                        </VisualBrush.Visual>
                    </VisualBrush>
                </Rectangle.Fill>
            </Rectangle>
        </Grid>

private void MasterImage_MouseWheel(object sender, MouseWheelEventArgs e)
{
System.Windows.Point centerPoint = e.GetPosition(MainPanel);

TransformGroup group = MainPanel.FindResource("ImageTransformResource") as TransformGroup;

ScaleTransform transform = group.Children[0] as ScaleTransform;

transform.CenterX = this.ActualWidth / 2;//centerPoint.X;
transform.CenterY = this.ActualHeight / 2;//centerPoint.Y;

transform.ScaleX += e.Delta * 0.001;
transform.ScaleY += e.Delta * 0.001;

if (transform.ScaleX < 0.2 || transform.ScaleY < 0.2)
{
transform.ScaleX += System.Math.Abs(e.Delta * 0.001);
transform.ScaleY += System.Math.Abs(e.Delta * 0.001);
}

if (transform.ScaleX > 2.0 || transform.ScaleY > 2.0)
{
transform.ScaleX -= Math.Abs(e.Delta * 0.001);
transform.ScaleY -= Math.Abs(e.Delta * 0.001);
}
}

private void MasterImage_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
System.Windows.Shapes.Rectangle rectangle = sender as System.Windows.Shapes.Rectangle;
if (rectangle == null)

return;


rectangle.ReleaseMouseCapture();
m_IsMouseLeftButtonDown = false;
}



private System.Windows.Point m_PreviousMousePoint;

private void MasterImage_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
System.Windows.Shapes.Rectangle rectangle = sender as System.Windows.Shapes.Rectangle;

if (rectangle == null)

return;

rectangle.CaptureMouse();

m_IsMouseLeftButtonDown = true;
m_PreviousMousePoint = e.GetPosition(rectangle);


}



private void MasterImage_MouseMove(object sender, MouseEventArgs e)
{

System.Windows.Shapes.Rectangle rectangle = sender as System.Windows.Shapes.Rectangle;

if (rectangle == null)
return;



if (m_IsMouseLeftButtonDown)
DoImageMove(rectangle, e);

}



private void DoImageMove(System.Windows.Shapes.Rectangle rectangle, MouseEventArgs e)
{

//Debug.Assert(e.LeftButton == MouseButtonState.Pressed);

if (e.LeftButton != MouseButtonState.Pressed)

return;

TransformGroup group = MainPanel.FindResource("ImageTransformResource") as TransformGroup;

TranslateTransform transform = group.Children[1] as TranslateTransform;

System.Windows.Point position = e.GetPosition(rectangle);

transform.X += position.X - m_PreviousMousePoint.X;
transform.Y += position.Y - m_PreviousMousePoint.Y;

m_PreviousMousePoint = position;
}


private void Window_Loaded(object sender, RoutedEventArgs e)
{



TransformGroup group = MainPanel.FindResource("ImageTransformResource") as TransformGroup;
ScaleTransform transform = group.Children[0] as ScaleTransform;
transform.CenterX = this.ActualWidth / 2;//centerPoint.X;
transform.CenterY = this.ActualHeight / 2;//centerPoint.Y;
transform.ScaleX = 0.8;
transform.ScaleY = 0.8;
}

奇怪的是，在pc上鼠标操作很正常，但是在pad上触摸操作完全不行，连移动都失灵了。
请问有什么好的办法兼容pad吗