使用Silverlight DeepZoom拖拽可以将MultiScaleImage拖出屏幕

Question

我有一些问题，我希望有人能回答这个问题。我有一个Deep Zoom项目，我使用了标准的(deep zoom composer)项目，它在MultiScaleImage控件上放置了一个DeepZommInitializer行为。我正在尝试限制拖动，以确保用户不会将图像拖出屏幕(因此无法找到图像)。我确实添加了一个Home按钮，它会将图像以1的缩放比例带回起始位置。不管怎样，这是我目前拥有的代码(我已经在互联网上寻找答案)。

        // msi is the multiscale image
        msi.MouseLeftButtonDown += delegate(object sender, MouseButtonEventArgs e)
        {
            lastMouseDownPos = e.GetPosition(msi); // class level var
            lastMouseViewPort = msi.ViewportOrigin; // class level var

            mouseDown = true; // class level var

            msi.CaptureMouse();
        };

        msi.MouseMove += delegate(object sender, MouseEventArgs e)
        {
            lastMousePos = e.GetPosition(msi);

            if (duringDrag) 
            {
                Point newPoint = lastMouseViewPort;

                newPoint.X += (lastMouseDownPos.X - lastMousePos.X) / msi.ActualWidth * msi.ViewportWidth;
                newPoint.Y += (lastMouseDownPos.Y - lastMousePos.Y) / msi.ActualWidth * msi.ViewportWidth;

                var limits = new Rect(new Point(1, 1 / msi.AspectRatio), new Point(-1, -1 / msi.AspectRatio));

                if (newPoint.X > limits.Right * .999)
                {
                    newPoint.X += (-2 * (lastMouseDownPos.X - lastMousePos.X)) / msi.ActualWidth * msi.ViewportWidth; // Reverses direction when going off left

                }

                if (newPoint.Y > limits.Bottom * .999)
                {
                    newPoint.Y += (-2 * (lastMouseDownPos.Y - lastMousePos.Y)) / msi.ActualWidth * msi.ViewportWidth; // Reverses direction when going off top of screen
                }

                msi.ViewportOrigin = lastMouseViewPort = newPoint;
                lastMouseDownPos = lastMousePos;
            }
        };

我真的需要一个适用于右边和底部的解决方案，但是当我放大所有的值时，所有的值都会改变。如果缩放级别是1，我的limit代码就可以工作。我不敢相信在互联网上找不到它！但是，当缩放发生变化时，一切都会消失( newPoint的值不在我期望的范围内)。任何帮助都是很棒的！

Answer 1

就这样，我自己想明白了(几周后终于明白了)。

以下是答案(简单地更改鼠标移动事件，如下所示)：

        msi.MouseMove += delegate(object sender, MouseEventArgs e)
        {
            lastMousePos = e.GetPosition(msi);

            if (duringDrag) 
            {
                Point newPoint = lastMouseViewPort;

                newPoint.X += (lastMouseDownPos.X - lastMousePos.X) / msi.ActualWidth * msi.ViewportWidth;
                newPoint.Y += (lastMouseDownPos.Y - lastMousePos.Y) / msi.ActualWidth * msi.ViewportWidth;
                var limits = new Rect(new Point(1, 1 / msi.AspectRatio), new Point(-1 / Settings.ZoomLevel, -1 / msi.AspectRatio / Settings.ZoomLevel));

                if (newPoint.X < limits.Left * .999)
                {
                    newPoint.X += (-2*(lastMouseDownPos.X - lastMousePos.X)) / msi.ActualWidth * msi.ViewportWidth;  // we went off right so reverse X direction

                }
                if (newPoint.X > limits.Right * .999)
                {
                    newPoint.X += (-2 * (lastMouseDownPos.X - lastMousePos.X)) / msi.ActualWidth * msi.ViewportWidth; // we went off left so reverse X direction
                }
                if (newPoint.Y < limits.Top * .999)
                {
                    newPoint.Y += (-2*(lastMouseDownPos.Y - lastMousePos.Y)) / msi.ActualWidth * msi.ViewportWidth;  // we went off Bottom so reverse direction
                }
                if (newPoint.Y > limits.Bottom * .999)
                {
                    newPoint.Y += (-2 * (lastMouseDownPos.Y - lastMousePos.Y)) / msi.ActualWidth * msi.ViewportWidth; // we went off Top so reverse direction
                }
                msi.ViewportOrigin = lastMouseViewPort = newPoint;
                lastMouseDownPos = lastMousePos;

                msi.SendMovedZoomMsg(Settings.ZoomLevel, newPoint, myClassName);
            }
        };

这可能不会完全限制图像，但它会将图像保留在屏幕上，并且用户很可能会停止尝试向错误的方向移动

Answer 2

我相信下面的代码正确地确定了ViewportOrigin是否在屏幕上留下了图像的某一部分。(ImageCtrl是MultiScaleImage的类变量)。

    private bool IsValidOrigin(Point point)
{
  var limits = new Rect(
                 new Point(-0.95 * ImageCtrl.ViewportWidth, -0.85 * ImageCtrl.ViewportWidth/ ImageCtrl.AspectRatio), 
                 new Point(0.95, 0.85/ImageCtrl.AspectRatio));
  return limits.Contains(point);
}