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因此，当您使用 PhotoChooserTask 时，我试图实现类似于原生裁剪器的效果。如果您不熟悉，背景中有一个顶部有边框的图像，并且图像在进出边框时似乎会改变不透明度。下面的代码工作正常，但不是很流畅（剪辑的图像稍微落后于拖动运动）。有什么方法可以加快剪辑或更改内容以减少延迟？我有以下 XAML：

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0" HorizontalAlignment="Center" VerticalAlignment="Center">
    <Grid x:Name="cropContainer" Width="375" MouseLeftButtonDown="cropContainer_MouseLeftButtonDown" MouseLeftButtonUp="cropContainer_MouseLeftButtonUp" MouseMove="cropContainer_MouseMove">
        <Grid.RenderTransform>
            <TranslateTransform x:Name="cropTransform" />
        </Grid.RenderTransform>
        <Image x:Name="fullImage" Source="{Binding Image}" Opacity=".5" />
        <Image x:Name="clippedImage" Source="{Binding Image}">
            <Image.Clip>
                <RectangleGeometry Rect="0,0,375,267" />
            </Image.Clip>
        </Image>
    </Grid>
</Grid>
<Border x:Name="cropBorder" Grid.Row="1" BorderThickness="1" BorderBrush="White" Opacity="1" Height="267.90571169537624660018132366274" Width="375">
</Border>

这是滑动期间跟踪和剪辑的代码：

private Point _cropBorderOffset, _original, _newPosition;
private bool _moving;
private double _maxUp, _maxDown;

void Page_Loaded(object sender, RoutedEventArgs e)
{
    var transform = cropBorder.TransformToVisual(Application.Current.RootVisual);
    _cropBorderOffset = transform.Transform(new Point(0, 0));

    _maxDown = ((fullImage.ActualHeight - cropBorder.ActualHeight) / 2);
    _maxUp = -_maxDown;

    var rect = (clippedImage.Clip as RectangleGeometry).Rect;
    (clippedImage.Clip as RectangleGeometry).Rect = new Rect(rect.X, (fullImage.ActualHeight / 2) - 134, rect.Width, rect.Height);
}

private void cropContainer_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
    cropContainer.CaptureMouse();
    _original = e.GetPosition(cropBorder);
    _moving = true;
}

private void cropContainer_MouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
    cropContainer.ReleaseMouseCapture();
    _moving = false;
}

private void cropContainer_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
{
    _newPosition = e.GetPosition(cropBorder);

    if(_moving)
    {
        var deltaY = _newPosition.Y - _original.Y;

        var transform = fullImage.TransformToVisual(Application.Current.RootVisual);
        var fullImageOffset = transform.Transform(new Point(0, 0));

        var marginTop = deltaY;

        //Too far down
        if (marginTop > _maxDown)
        {
            marginTop = _maxDown;
        }
        //Too far up
        else if (marginTop < _maxUp)
        {
            marginTop = _maxUp;
        }

        cropTransform.Y = marginTop;

        var rect = (clippedImage.Clip as RectangleGeometry).Rect;
        (clippedImage.Clip as RectangleGeometry).Rect = new Rect(rect.X, _cropBorderOffset.Y - fullImageOffset.Y, rect.Width, rect.Height);
    }
}
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1 回答 1

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不是画两次图像，一次有裁剪，一次没有，你能不能简单地画半透明的矩形来挡住边，画一个白色的轮廓作为中心？这应该会大大减少延迟。

然后，您可以使用剪切矩形的左侧、顶部、宽度和高度，一旦选择了位置来实际在内存中进行裁剪。

于 2012-02-16T22:38:17.130 回答