Hello,

Is it possible to blend more than two pictures into each other? Im using
Alphablend to blend two pictures, but i dont get it working with more than
two pictures! Can someone help me with this??

Thx

Dennis

How is this 'not working', and what code are you using to draw them?  Is it that you're just not seeing the third image,
or the output is garbage?  Remember that if you're drawing three images on-top of one another each at 50% opacity then
the bottom image will not be particularly visible, perhaps this is the cause of the problem?

Draw image 1:
Background: 50%
Image 1: 50%

Draw image 2:
Background: 25%
Image 1: 25%
Image 2: 50%

Draw image 3:
Background: 12.5%
Image 1: 12.5%
Image 2: 25%
Image 3: 50%

To rectify this simply draw the first image at 100% opacity, the next at 50% and the third at 25% - you may want to play
around with these values to get the desired result.  The other option is to perform the blending yourself which would
give you a perfect ratio between the three images.
Hope this helps,

    Mike


- Microsoft Visual Basic MVP -
E-Mail: ED***@mvps.org
WWW: Http://EDais.mvps.org/

I tried blending first two images in each other, and afterwards i blended
another picture to the two blended images. This resulted in a weird blueisch
screen!?
Can you perhaps give me an example, because im struggling with this problem
for days, argh

Thx in advance
Dennis


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Im using the following code for blending 2 pictures:

##################################################
Const AC_SRC_OVER = &H0
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)

Sub overlay ()
Picture1.Picture = LoadPicture(App.Path & "\" & "framevideo1_1.jpg")
Picture2.Picture = LoadPicture(App.Path & "\" & "framevideo1_2.jpg")
Picture1.Visible = False


    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 = 150
        .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

#####################################################

Which line do i have to adjust to mix more than two pictures??

Thx
Dennis

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<code snipped>
Without knowing what your source images look like, I can't solve the
'blueisch screen' problem, however if you blend two inverted images together
you're more than likely going to get a greyish splodge so this could be the
cause.  Basically you just adjust your blend function for each image, here's
a slightly easier function for creating the blend function DWord without
requiring the UDT declaration or memory copy API:

'***
Private Function CreateBlendOp(ByVal inSourceConstantAlpha As Byte, _
    Optional ByVal inPerPixel As Boolean = False) As Long
    If (inPerPixel) Then CreateBlendOp = &H1000000
    CreateBlendOp = CreateBlendOp Or (inSourceConstantAlpha * &H10000)
End Function
'***

The first picture should be rendered with 50% opacity (255/100)*50 = 128 and
the next should be rendered with 25% opacity (255/100)*25 = 64.
Hope this helps,

    Mike


- Microsoft Visual Basic MVP -
E-Mail: ED***@mvps.org
WWW: Http://EDais.mvps.org/

Hello,

I solved the problem, i didnt declared that the Picture was working in
pixels (vbPixels).
At the moment im blending 10 pictures in each other. Im doing this by
calling 10 functions with the different pictures. Is there a way to mix the
pictures in one function (at once). So that i dont have to load every picture
separate??

Thx
Dennis

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You could write your own blend function which takes the average of all the
pixels at that position on each image, not sure if this is what you're after
though.  If you wanting a solution that blends 10 images in the same way as
AlphaBlend() works between 2 then there is no such thing.
Hope this helps,

    Mike


- Microsoft Visual Basic MVP -
E-Mail: ED***@mvps.org
WWW: Http://EDais.mvps.org/

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