在WinForms应用程序填充的橡胶带

问题描述

我怎么可以得出一个零透明度橡皮筋过窗户，0.3不透明形成的？
（橡皮筋是例如

how can i draw a zero opacity rubber band over a windows form with 0.3 opacity?(The rubber band is made after a Microsoft example

更新：的

Update:

我需要橡皮筋的工作像一个面具。如果你使用敬或任何其他屏幕截图工具，你会看到正是我需要的，当你试图做一个屏幕截图的事：屏幕变成半透明的，当你做出选择，你会看到0混浊选择

I need that rubber band to work something like a mask. If you use Jing or any other screen shot tool, you will see EXACTLY what I need to do when do you try to make a screenshot: the screen goes semi-opaque and when you make the selection, you will see the 0 opacity selection

推荐答案

这是你要找的机器人？

    public Form1()
    {
        InitializeComponent();
        DoubleBuffered = true;
    }

    bool mouseDown = false;
    Point mouseDownPoint = Point.Empty;
    Point mousePoint = Point.Empty;

    protected override void OnMouseDown(MouseEventArgs e)
    {
        base.OnMouseDown(e);
        mouseDown = true;
        mousePoint = mouseDownPoint = e.Location;
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        base.OnMouseUp(e);
        mouseDown = false;
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);
        mousePoint = e.Location;
        Invalidate();
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        if (mouseDown)
        {
            Region r = new Region(this.ClientRectangle);
            Rectangle window = new Rectangle(
                Math.Min(mouseDownPoint.X, mousePoint.X),
                Math.Min(mouseDownPoint.Y, mousePoint.Y),
                Math.Abs(mouseDownPoint.X - mousePoint.X),
                Math.Abs(mouseDownPoint.Y - mousePoint.Y));
            r.Xor(window);
            e.Graphics.FillRegion(Brushes.Red, r);
            Console.WriteLine("Painted: " + window);
        }
    }

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