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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

Update:

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

Community
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andySF
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    Zero opacity means fully transparent. I think you mean opaque. – SLaks Jan 14 '10 at 15:28
  • how will you be able to see it? – Matt Jan 14 '10 at 15:29
  • By the way, that article is wrong. You can simply call `ControlPaint.DrawReversibleFrame`: http://msdn.microsoft.com/en-us/library/system.windows.forms.controlpaint.drawreversibleframe.aspx. (Although it didn't exist in .Net 1.0) – SLaks Jan 14 '10 at 15:30

4 Answers4

8

Is this the droid you were looking for?

    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);
        }
    }
Dearmash
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1

You need to use a partially opaque color when drawing:

Updated line from linked article, in the MyDrawReversibleRectangle method:

ControlPaint.DrawReversibleFrame( rc, Color.FromArgb(80, 120, 120, 120), FrameStyle.Dashed );
Oded
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  • sorry but that is not working. i don't know why but here is a screen shoot http://screencast.com/t/NjM1NjBkZTc . The grayed color is from my .4 opacity full screen form and the dashed rectangle is the DrawReversibleFrame method that completely ignores the backcolor parameter. Thank you and excuse my English. – andySF Jan 15 '10 at 06:45
1

I used the code that @Dearmash supplied in the screen capture utility that comes with my open source app BugTracker.NET. The app isn't very big, so if you are doing screen capture stuff, it might be a good starting point. More info here:

http://ifdefined.com/blog/post/Screen-capture-utility-in-C-NET.aspx

Corey Trager
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0

Just use an additional form, without showing it in the taskbar, or other Form-options. Set the region of the form that it only shows the rubber band. And make sure both windows behave as if it was one window (moving, closing,...). I know it's not an elegant way, but with a little work it can produce good results. You can make sure that the form is on top in the form-hierarchy and still doen't receive focus.

By setting the region good, all events will go to the other form.

That's the way I worked out an equivalent problem (I don't say it's a good solution, but it works)

Willem Van Onsem
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