在应用程序中模拟 WP7 相机胶卷缩放和拖动功能

Question

我试图让用户拍摄包含文本的图片，以便用户可以突出显示他们想要运行 OCR 的文本。

我已经把图片部分放下来了，我可以显示图像了。然后，我希望用户能够捏合缩放，然后滑动以移动图片，就像相机胶卷对单张照片所做的那样。这将使用户能够更清楚地看到他们想要运行 OCR 的文本。目前我只能使用捏变焦功能，但效果非常糟糕。

private Popup popup = new Popup { IsOpen = true };
private Grid grid = new Grid { Width = 480, Height = 800 };
private Image backgroundImage = new Image
{
    Stretch = Stretch.Uniform,
    RenderTransformOrigin = new Point(.5, .5),
    RenderTransform = new CompositeTransform()
};

void OCRSelection_Loaded(object sender, RoutedEventArgs e)
{
   this.grid.Children.Add(this.backgroundImage);
   this.popup.Child = this.grid;
   var gl = GestureService.GetGestureListener(this.backgroundImage);
   gl.PinchStarted += new EventHandler<PinchStartedGestureEventArgs(gl_PinchStarted);
   gl.PinchDelta += new EventHandler<PinchGestureEventArgs>(gl_PinchDelta);
}

private void gl_PinchStarted(object sender, PinchStartedGestureEventArgs e)
{
    _oldFinger1 = e.GetPosition(this.backgroundImage, 0);
    _oldFinger2 = e.GetPosition(this.backgroundImage, 1);
    _oldScaleFactor = 1;
}

private void gl_PinchDelta(object sender, PinchGestureEventArgs e)
{
        var scaleFactor = e.DistanceRatio / _oldScaleFactor;

        var currentFinger1 = e.GetPosition(this.backgroundImage, 0);
        var currentFinger2 = e.GetPosition(this.backgroundImage, 1);

        var translationDelta = GetTranslationDelta(
            currentFinger1,
            currentFinger2,
            _oldFinger1,
            _oldFinger2,
            ImagePosition,
            scaleFactor);

        _oldFinger1 = currentFinger1;
        _oldFinger2 = currentFinger2;
        _oldScaleFactor = e.DistanceRatio;

        UpdateImage(scaleFactor, translationDelta);
}
private void UpdateImage(double scaleFactor, Point delta)
{
    TotalImageScale *= scaleFactor;
    ImagePosition = new Point(ImagePosition.X + delta.X, ImagePosition.Y + delta.Y);

    var transform = (CompositeTransform)this.backgroundImage.RenderTransform;
        transform.ScaleX = TotalImageScale;
        transform.ScaleY = TotalImageScale;
        transform.TranslateX = ImagePosition.X;
        transform.TranslateY = ImagePosition.Y;
    }

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);
}

我从 WindowsPhoneGeek 找到了这段代码，因此我不会将其归功于 100%。实际上，当我缩小太远时，我会丢失图片，并且当我缩小时，它也会因为弹到不同的边缘而变得疯狂。我相信这可能是因为我必须将图像旋转 90 度。

我还想让用户用拖动手势移动图片。有人做过这样的事情或者有什么建议吗？

另外，这只是我使用 WP7 的第二周，所以我可能只是错过了一些简单的东西。提前致谢。

Answer 1

http://multitouch.codeplex.com/ 上有一些预先存在的行为，这可能是一个更简单的解决方案满足您的需求。