Solved

Imagelist shows blank bitmaps

Posted on 2008-10-08
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Last Modified: 2012-05-05
This strikes me as odd - I create a small in-memory bitmap, and draw a single character with a background color on it. I then transfer this into an Imagelist control. However, when I transfer the imagelist.image(x) to a location in a picturebox, only the background color of the image shows up.

I know that the bitmap was created correctly, because if I use "bmp1.save(filename)" then take the file and read it into an image ("dim g as image = image.fromfile(filename)") then load g into the imagelist, it works great.

Can anyone tell me why it doesn't transfer properly to the imagelist unless I save it to disk and read it back?  Thanks!!


Dim bmp1 As New Bitmap(CellWidth, CellHeight, System.Drawing.Imaging.PixelFormat.Format24bppRgb)
 
For i = 1 To CellWidth
  For l = 1 To CellHeight
  'draw the '1's' as black
   If Mid$(CellString(i), l, 1) = "1" Then
     bmp1.SetPixel(i - 1, CellHeight - l, Color.Black)
   Else
     bmp1.SetPixel(i - 1, CellHeight - l, Color.DarkGoldenrod)
   End If
  Next l
Next i
 
IList1A.Images.Add(bmp1)

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Question by:LongDave
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8 Comments
 
LVL 55

Expert Comment

by:Jaime Olivares
ID: 22673239
try with the following:

yourImgList.ImageSize = new System.Drawing.Size(CellWidth, CellHeight)
yourImgList.Images.Add(bmp1)
yourImgList.TransparentColor = Color.DarkGoldenrod  'optional

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Author Comment

by:LongDave
ID: 22673676
Nope - that didn't do it. The wierd thing is that it seems that saving the bmp to a file and then calling it back somehow transforms it so that it loads properly in the Imagelist control. Any other ideas?

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LVL 85

Expert Comment

by:Mike Tomlinson
ID: 22673845
Does this make a diff?
        Dim bmp1 As New Bitmap(cellWidth, cellHeight, System.Drawing.Imaging.PixelFormat.Format24bppRgb)
        Dim G As Graphics = Graphics.FromImage(bmp1)
        G.Clear(Color.Goldenrod)
        For i = 1 To cellWidth
            For l = 1 To cellHeight
                'draw the '1's' as black
                If Mid$(CellString(i), l, 1) = "1" Then
                    G.FillRectangle(Brushes.Black, New Rectangle(i - 1, cellHeight - l, 1, 1))
                End If
            Next l
        Next i
        G.Dispose()
        IList1A.Images.Add(bmp1)

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Author Comment

by:LongDave
ID: 22673947
OK!! That did it! But I still don't see why the use of the bmp directly to the imagelist didn't work properly. Any ideas? I'd really like to understand why. But I will issue you the points - I just didn't want to close the question before your answer.
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LVL 85

Accepted Solution

by:
Mike Tomlinson earned 500 total points
ID: 22674055
I really don't have a TECHNICAL answer for you sorry...just haven't really seen anyone using Bitmap.SetPixel() and I knew that my method would work...   =\

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Author Closing Comment

by:LongDave
ID: 31504403
Hi, Idle_Mind ... This is the 2nd time you've helped me. Thanks a lot! Your solution looks like it works fine - but I wish I knew WHY the other didn't!  :(
Oh, well!
0
 
LVL 85

Expert Comment

by:Mike Tomlinson
ID: 22674227
A simple test using your original technique worked for me...not sure what you did wrong:
Public Class Form1
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim CellWidth As Integer = 5
        Dim CellHeight As Integer = 5
 
        Dim pixels As String = "11111,00100,00100,00100,11111;10001,11011,10101,10001,10001"
        For Each charSig As String In pixels.Split(";")
            Dim bmp As New Bitmap(CellWidth, CellHeight, System.Drawing.Imaging.PixelFormat.Format24bppRgb)
            Dim rows() As String = charSig.Split(",")
            For y As Integer = 0 To rows.GetUpperBound(0)
                For x As Integer = 0 To rows(y).Length - 1
                    If rows(y).Substring(x, 1) = "1" Then
                        bmp.SetPixel(x, y, Color.Black)
                    Else
                        bmp.SetPixel(x, y, Color.DarkGoldenrod)
                    End If
                Next
            Next
            ImageList1.Images.Add(bmp)
        Next
        PictureBox1.Image = ImageList1.Images(0)
        PictureBox2.Image = ImageList1.Images(1)
    End Sub
 
End Class

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IM-Chars.jpg
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Author Comment

by:LongDave
ID: 22674270
Wierd - thanks for the input though. I was using the DrawImage function to place the chars in the picturebox, but I don't know why that would have made any difference (I'm sure it did not).

But thanks again - hope I don't have to bug you too often! :)
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