Windows Store App放大镜
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20-12-2019 - |
题
我正在研究Windows 8.1的绘图应用程序,需要一种简单的方式来显示用户触摸的区域。显然,在使用手指时,很难看到你在哪里画画。我需要做的是能够将目标元素呈现为位图,并将其显示给用户,以便它们可以看到它们在绘制位置。我想到的是在下面的答案。
解决方案
代码如下。要使用它,只需在XAML(或编程方式)中添加控件,无论您想要哪个,并将目标属性设置为要预览的控件。
例如,在我的情况下,我在webview上绘制,所以我将WebView设置为目标,并将放大镜添加为兄弟姐妹。public class Magnifier : Grid
{
public Magnifier() : base()
{
this.Canvas = new Canvas();
Border border = new Border();
border.HorizontalAlignment = HorizontalAlignment.Left;
border.VerticalAlignment = VerticalAlignment.Top;
border.Child = this.Canvas;
border.BorderBrush = new SolidColorBrush(Colors.Red);
border.BorderThickness = new Thickness(10);
border.Background = new SolidColorBrush(Colors.Black);
this.Children.Add(border);
this.border = border;
}
public async Task<object> Update(int x, int y)
{
this.Visibility = Visibility.Visible;
// changes the amount of magnification
int magnification = 2;
// render the preview of the target
RenderTargetBitmap bitmap = new RenderTargetBitmap();
await bitmap.RenderAsync(this.Target);
this.Canvas.Width = this.PreviewWidth;
this.Canvas.Height = this.PreviewHeight;
double w = this.PreviewWidth / (2 * magnification);
double h = this.PreviewHeight / (2 * magnification);
ImageBrush brush = new ImageBrush();
brush.ImageSource = bitmap;
double scaleX = this.Target.ActualWidth / this.PreviewWidth;
double scaleY = this.Target.ActualHeight / this.PreviewHeight;
TransformGroup transform = new TransformGroup();
TranslateTransform translate = new TranslateTransform();
translate.X = -(x - w) / scaleX;
translate.Y = -(y - h) / scaleY;
transform.Children.Add(translate);
ScaleTransform scale = new ScaleTransform();
scale.ScaleX = scaleX * magnification;
scale.ScaleY = scaleY * magnification;
transform.Children.Add(scale);
brush.Transform = transform;
Rectangle rect = new Rectangle();
rect.Width = this.PreviewWidth;
rect.Height = this.PreviewHeight;
rect.Fill = brush;
this.Canvas.Children.Clear();
this.Canvas.Children.Add(rect);
Ellipse centerDot = new Ellipse();
centerDot.Width = 6;
centerDot.Height = 6;
centerDot.Fill = new SolidColorBrush(Colors.Red);
Canvas.SetLeft(centerDot, this.PreviewWidth / 2 - 3);
Canvas.SetTop(centerDot, this.PreviewHeight / 2 - 3);
this.Canvas.Children.Add(centerDot);
return null;
}
public Canvas Canvas { get; set; }
public int PreviewWidth { get; set; }
public int PreviewHeight { get; set; }
private Border border = null;
public FrameworkElement Target { get; set; }
}
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