Question

I would like to display a larger image on a windows phone 7 device. I need to be able to zoom in and out using multi-touch gesture. I was wondering if there is any control that can do this out of the box in the Windows Phone 7 SDK?

Answer 1

If you don’t want to use DeepZoom, you could also use a ViewBox to contain the Image, and listen for the pinch touch gestures/events and zoom in and out of the ViewBox using a RenderTransform.

Below is some code that I used for a Silverlight app, which with some work could be changed to react to Pinch and touch gestures instead of mousewheel + click/drag events. It might be possible to also change the amount of zoom depending on the “strength” of the pinch gesture.

For a viewbox defined in XAML:

    <Border Name="viewboxBackground" Background="Black">
            <Viewbox Name="viewboxMain">
                <!--your content here -->
            </Viewbox>
    </Border>   

Codebehind:

    #region Pan and Zoom Events and Handlers

    void MouseClickHandler(object sender, MouseButtonEventArgs e)
    {
        _mouseClickPos = e.GetPosition(viewboxBackground);
        bMoving = true;
    }

    void MouseMoveHandler(object sender, MouseEventArgs e)
    {

        if (bMoving)
        {
            //get current transform
            CompositeTransform transform = viewboxMain.RenderTransform as CompositeTransform;

            Point currentPos = e.GetPosition(viewboxBackground);
            transform.TranslateX += (currentPos.X - _mouseClickPos.X);
            transform.TranslateY += (currentPos.Y - _mouseClickPos.Y);

            viewboxMain.RenderTransform = transform;

            _mouseClickPos = currentPos;
        }
    }

    void MouseReleaseHandler(object sender, MouseButtonEventArgs e)
    {
        bMoving = false;
    }

    void MouseWheelZoom(object sender, MouseWheelEventArgs e)
    {
        if (e.Delta > 0)
        {
            _zoomMultiplier += _zoomRate;
            ApplyZoomTransform(viewboxMain, _zoomMultiplier, new Point(viewboxMain.ActualWidth / 2, viewboxMain.ActualHeight / 2));
        }
        else if (e.Delta < 0 && _zoomMultiplier > 1)
        {
            _zoomMultiplier -= _zoomRate;
            ApplyZoomTransform(viewboxMain, _zoomMultiplier, new Point(viewboxMain.ActualWidth / 2, viewboxMain.ActualHeight / 2));
        }
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="element"></param>
    /// <param name="iZoomFactor"></param>
    /// <param name="zoomCenter">If provided, the zoom will be centered around the given position.</param>
    void ApplyZoomTransform(UIElement element, double iZoomFactor, Point? zoomCenter)
    {
        //get current transform
        CompositeTransform transform = viewboxMain.RenderTransform as CompositeTransform;

        if (zoomCenter != null)
        {
            transform.CenterX = zoomCenter.GetValueOrDefault().X;
            transform.CenterY = zoomCenter.GetValueOrDefault().Y;
        }
        transform.ScaleX = iZoomFactor;
        transform.ScaleY = iZoomFactor;

        element.RenderTransform = transform;
    }

    #endregion