有时候需要实现类似于QQ截图那样的选择区域功能,这里的区域可以是一条线,圆,矩形等等
实现原理就是一个Canvas做蒙板,然后canvas的三个事件,MouseLeftButtonDown,MouseMove,MouseLeftButtonUp。非常easy!
首先,你要有个canvas
<Canvas Name="videocanvas" Height="" Width="" Background="Transparent" MouseMove="image_MouseMove" MouseLeftButtonDown="Mask_MouseLeftButtonDown" MouseLeftButtonUp="Mask_MouseLeftButtonUp"/>
然后实现他的事件,在之前我们先决定一下到底是什么形状的区域。
public static Shape CreateShape()
{
//矩形区域
return new System.Windows.Shapes.Rectangle() { Fill = null, Stroke = System.Windows.Media.Brushes.Red, StrokeThickness = };
//圆形区域
//return new System.Windows.Shapes.Ellipse() { Fill = null, Stroke = System.Windows.Media.Brushes.Red, StrokeThickness = 1 }; }
然后实现三个事件
bool drawFlag = false;
Shape insertShape;
System.Windows.Point startPosition; private void Mask_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
insertShape = CreateShape();
if (insertShape != null)
{
drawFlag = true;
Canvas board = sender as Canvas;
board.Children.Clear();
startPosition = e.GetPosition(board);
insertShape.Opacity = ;
Canvas.SetLeft(insertShape, e.GetPosition(board).X);
Canvas.SetTop(insertShape, e.GetPosition(board).Y);
board.Children.Add(insertShape);
}
} private void image_MouseMove(object sender, MouseEventArgs e)
{
Canvas board = sender as Canvas;
if (drawFlag && insertShape != null)
{
if (e.GetPosition(board).X > startPosition.X)
{
insertShape.Width = e.GetPosition(board).X - startPosition.X; }
else
{
insertShape.Width = startPosition.X - e.GetPosition(board).X;
Canvas.SetLeft(insertShape, e.GetPosition(board).X);
}
if (e.GetPosition(board).Y > startPosition.Y)
{
insertShape.Height = e.GetPosition(board).Y - startPosition.Y;
}
else
{
insertShape.Height = startPosition.Y - e.GetPosition(board).Y;
Canvas.SetTop(insertShape, e.GetPosition(board).Y);
}
}
} private void Mask_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
drawFlag = false;
if (insertShape != null)
{
insertShape.Opacity = ;
System.Windows.Point p = e.GetPosition(sender as Canvas);
Canvas.SetLeft(insertShape, e.GetPosition(board).X);
Canvas.SetTop(insertShape, e.GetPosition(board).Y);
}
}
本来还想做个多边形的例子,水平有限,没达到我想要的效果。研究研究再发。