transparent picture boxes (API?)

i have 2 identical picture boxes one directly on top of the other, named Upper and Lower.

can somebody please tell me a way to make the Upper picturebox transparent, so that the Lower picture shows through. the reason for this is so i can have a circle moving around on the Upper and drawing a line behind it on the Lower, i dont want the circle to "damage" the image on Lower.

I know there is an API thingy for this, but i dont have a clue how to use API stuff.

(analogy...) the circle looks like it is on a overhead projector overlay.

I would be MEGA thankful!


------------------

Wossname,
Email me: [email protected] :)

[This message has been edited by wossname (edited 12-12-1999).]

in a .bas module put this code:

Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long) As Long
Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
Declare Function SetWindowRgn Lib "user32" (ByVal hwnd As Long, ByVal hRgn As Long, ByVal bRedraw As Long) As Long
Declare Function CombineRgn Lib "gdi32" (ByVal hDestRgn As Long, ByVal hSrcRgn1 As Long, ByVal hSrcRgn2 As Long, ByVal nCombineMode As Long) As Long

Sub PicLoad(pic As PictureBox)

Dim maskcolor As Long 'declare variable for the transparent color

'set transparent color as great pink
maskcolor = RGB(255, 0, 255)

'perform function to make pictures transparent
TransBack 0, 0, pic.Width / 15, pic.Height / 15, maskcolor, pic.hdc, pic.hwnd

End Sub

Private Sub TransBack(ByVal xstart As Long, ByVal ystart As Long, ByVal xend As Long, ByVal yend As Long, ByVal bgcolor As Long, ByVal thdc As Long, ByVal thWnd As Long)

'declare region variables
Dim rgn2 As Long, rgn3 As Long, rgn4 As Long

'declare substitute variables for the function parameters
Dim Top As Long, Left As Long, Right As Long, Bottom As Long, temptop As Long

'create some region buffers
rgn = CreateRectRgn(0, 0, 0, 0)
rgn2 = CreateRectRgn(0, 0, 0, 0)
rgn3 = CreateRectRgn(0, 0, 0, 0)

'this loop picks out the transparent colors,
'there MUST be three loops or Windows has a hard
'time handling the complex regions

Left = xstart
Right = (xend - xstart) + 1: Bottom = (yend - ystart) + 1

Do While Left < Right 'go through and scan left to right
Top = ystart
Do While Top < Bottom 'go through and scan top to botom
If GetPixel(thdc, Left, Top) <> bgcolor Then
temptop = Top
Do While GetPixel(thdc, Left, Top + 1) <> bgcolor
Top = Top + 1
If Top = Bottom Then Exit Do
Loop
rgn4 = CreateRectRgn(Left, temptop, Left + 1, Top + 1)
CombineRgn rgn3, rgn2, rgn2, 5
CombineRgn rgn2, rgn4, rgn3, 2
DeleteObject rgn4
End If
Top = Top + 1
Loop
CombineRgn rgn3, rgn, rgn, 5
CombineRgn rgn, rgn2, rgn3, 2
DoEvents
Left = Left + 1
Loop

DeleteObject rgn2
SetWindowRgn thWnd, rgn, True

End Sub
----------------------
then in your form put this code:

picload(picture1)

(picture1 = name of your picturebox)

hope this helps. happy programming!!

--michael

Thank you funkheads, this is what I was looking for too.

However, I couldn't get it to work and there are also bits of code I couldn't understand. So I persevered and with through trial and error I got it to work.

I use VB6 and here are the changes I made:
Changed each occurrence of &lt;&gt; TO <> (not equal to)

Changed each occurrence of &lt; TO < (less than)

Changed picload(picture1) TO picload picture1 (removed brackets)

Moved Top = ystart TO line BEFORE previous line (Do While Left &lt; Right 'go through and scan left to right)

Hope this helps
regards
Trevor