Alphablend again

[Yok]

What is BlendFlags and AlphaFormat used for?

[jim mcnamara]

AlphaBlend is used to display bitmaps with transparency onto a device context - ie, kind of overwrite the original picture.

From www.allapi.net

'This project requires two picture boxes
'Both picture boxes should contain a picture
Private Type BLENDFUNCTION
  BlendOp As Byte
  BlendFlags As Byte
  SourceConstantAlpha As Byte
  AlphaFormat As Byte
End Type
Private Declare Function AlphaBlend Lib "msimg32.dll" (ByVal hdc As Long, ByVal lInt As Long, ByVal lInt As Long, ByVal lInt As Long, ByVal lInt As Long, ByVal hdc As Long, ByVal lInt As Long, ByVal lInt As Long, ByVal lInt As Long, ByVal lInt As Long, ByVal BLENDFUNCT As Long) As Long
Private Declare Sub RtlMoveMemory Lib "kernel32.dll" (Destination As Any, Source As Any, ByVal Length As Long)
Private Sub Form_Load()
    'KPD-Team 2000
    'URL: http://www.allapi.net/
    'E-Mail: [email protected]
    Dim BF As BLENDFUNCTION, lBF As Long
    'Set the graphics mode to persistent
    Picture1.AutoRedraw = True
    Picture2.AutoRedraw = True
    'API uses pixels
    Picture1.ScaleMode = vbPixels
    Picture2.ScaleMode = vbPixels
    'set the parameters
    With BF
        .BlendOp = AC_SRC_OVER
        .BlendFlags = 0
        .SourceConstantAlpha = 128
        .AlphaFormat = 0
    End With
    'copy the BLENDFUNCTION-structure to a Long
    RtlMoveMemory lBF, BF, 4
    'AlphaBlend the picture from Picture1 over the picture of Picture2
    AlphaBlend Picture2.hdc, 0, 0, Picture2.ScaleWidth, Picture2.ScaleHeight, Picture1.hdc, 0, 0, Picture1.ScaleWidth, Picture1.ScaleHeight, lBF
End Sub

BlendFlags is a part of a UDT, as you see in the code above.
To get values for BlendFlags and the other members of BLENDFUNCTION, go to http://www.msdn.microsoft.com