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Store picturebox.image in an imagelist in VB.NET

Posted on 2008-10-03
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Last Modified: 2010-04-21
Hi, experts -
I'm sure I'm just missing something ridiculously simple. I'm drawing a character in a picturebox, using Graphics objects associated with 2 pictureboxes (PB and PB2). After the character is drawn, I'm trying to put the picturebox image into an imagelist control. The imagelist is supposed to take an image of type "System.Drawing.Image" - which is what the picture box image should be (I assume). Yet in the line that is "IList1A.Images.Add (PB.Image)", I get an error saying that "Value can not be null" for PB.Image.

I just got through writing pixels on the bitmap of the PB, I don't see where it should be null. Can someone tell me what I'm doing wrong?

Thanks!

Dim g As Graphics = System.Drawing.Graphics.FromHwnd(PB.Handle)

                        Dim g1 As Graphics = System.Drawing.Graphics.FromHwnd(PB2.Handle)
 

                        For i = 1 To CellWidth

                            For l = Pointer1 + 1 To Pointer1 + 1 + CellHeight

                                'draw the '1's' as black

                                If Mid$(CellString(i), l, 1) = "1" Then

                                    g.DrawEllipse(Pens.Black, i - 1, CellHeight - (l - Pointer1), 1, 1)

                                    g1.DrawEllipse(Pens.Black, i - 1, CellHeight - (l - Pointer1), 1, 1)

                                Else

                                    g.DrawEllipse(Pens.Khaki, i - 1, CellHeight - (l - Pointer1), 1, 1)

                                    g1.DrawEllipse(Pens.DarkKhaki, i - 1, CellHeight - (l - Pointer1), 1, 1)

                                End If

                            Next l

                        Next i
 

                        ICount = ICount + 1

                        If j = 0 Then

                            IList1A.Images.Add(PB.Image)

                            IList1B.Images.Add(PB2.Image)

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Question by:LongDave
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Expert Comment

by:Mike Tomlinson
Comment Utility
"I just got through writing pixels on the bitmap of the PB, I don't see where it should be null. Can someone tell me what I'm doing wrong?"

No, essentially what you did was draw on TOP of the PictureBox...sorta like drawing in the same layer that would draw its Border if that Style was enabled:

    Dim g As Graphics = System.Drawing.Graphics.FromHwnd(PB.Handle)

If you want to draw on the Image that the PictureBox is DISPLAYING, then you would need:

    Dim g As Graphics = System.Drawing.Graphics.FromImage(PB.Image)

*** BUT *** this assumes that you have actually ASSIGNED a valid Image to the PictureBoxes Image() Property!

By default, a PictureBox doesn't display anything and the Image() Property would return "Nothing"...
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Accepted Solution

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Mike Tomlinson earned 500 total points
Comment Utility
...what is the end goal here?...the nature of your code makes me wonder if you really need a PictureBox at all!  =\

You probably wanted something more like this:

    Dim bmp As New Bitmap(someWidth, someHeight)
    Dim G As Graphics = Graphics.FromImage(bmp)
    ' ... draw with "G" ...
    G.Dispose()
    IList1A.Images.Add(bmp)
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Author Closing Comment

by:LongDave
Comment Utility
Idle_Mind .... Not so Idle, m'man. Excellent suggestions - and it appears to work great! Many thanks .. all points are yours.
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