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Drawing a Bounding Box rectangle in vb.net 2005

Posted on 2009-05-14
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Last Modified: 2013-11-27
Hello,

I never thought I'd actually be writing on how to do this, but I am having nothing but trouble getting this to work.

I have a picture on the screen.  I want to give the user the ability to crop the picture, so I have a crop button on the toolbar.  When cropping starts, I want the user to be able to click and drag around the area that they want to keep within the picture.  I would like to draw a rectangle AS they move the mouse.

What I'm running into is I can do the draw rectangle, but as the mouse moves, another rectangle is created and another, etc. so I end up with a series of rectangles rather than one when I'm all done.

In vb6 world, I used a "shape" to accomplish this and just kept moving the bottom right point of the shape.  I just don't know how to do this in vb.net 2005

Thanks so much
Gary H.
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Question by:garyhoffmann
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Mike Tomlinson earned 250 total points
ID: 24389440
Bare bones "rubberbanding" example in VB.Net 2005:
Public Class Form1
 
    Private RC As Rectangle
    Private screenPtA, screenPtB As Point
 
    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Left Then
            Dim pb As PictureBox = CType(sender, PictureBox)
            Cursor.Clip = pb.RectangleToScreen(pb.ClientRectangle)
            screenPtA = Cursor.Position
            screenPtB = screenPtA
            RC = NormalizedRC(screenPtA, screenPtB)
            ControlPaint.DrawReversibleFrame(RC, Color.Black, FrameStyle.Dashed)
        End If
    End Sub
 
    Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If e.Button = Windows.Forms.MouseButtons.Left Then
            ControlPaint.DrawReversibleFrame(RC, Color.Black, FrameStyle.Dashed)
            screenPtB = Cursor.Position
            RC = NormalizedRC(screenPtA, screenPtB)
            ControlPaint.DrawReversibleFrame(RC, Color.Black, FrameStyle.Dashed)
        End If
    End Sub
 
    Private Sub PictureBox1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        If e.Button = Windows.Forms.MouseButtons.Left Then
            Cursor.Clip = Nothing
            Dim pb As PictureBox = CType(sender, PictureBox)
            RC = pb.RectangleToClient(RC)
 
            MessageBox.Show(RC.ToString, "Client Crop Rectangle")
        End If
    End Sub
 
    Public Function NormalizedRC(ByVal ptA As Point, ByVal ptB As Point) As Rectangle
        Return New Rectangle(Math.Min(ptA.X, ptB.X), Math.Min(ptA.Y, ptB.Y), Math.Abs(ptA.X - ptB.X), Math.Abs(ptA.Y - ptB.Y))
    End Function
 
End Class

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Author Comment

by:garyhoffmann
ID: 24394485
Idle Mind - this is great.  Thank you.  But... (and there's always a but....)

What if the user realizes they started in the wrong place and wants to start over?  How do I remove the rectangle that's been drawn?

Thank you.
Gary.
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Author Comment

by:garyhoffmann
ID: 24394656
Idle Mind,

Never mind - I found my own answer based on your code.  Thanks again.

Gary
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LVL 85

Expert Comment

by:Mike Tomlinson
ID: 24396049
To clear the PB just issue a Refresh() and any existing bounding box will be cleared:

    PictureBox1.Refresh()
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