Transparent portrait on a background image

<!-- METADATA TYPE="typelib" UUID="{3CE48541-DE7A-4909-9314-9D0ED0D1CA5A}"-->
<%
Dim objPortrait, objBackground

Set objPortrait = Server.CreateObject("GraphicsMill.Bitmap")
Set objBackground = Server.CreateObject("GraphicsMill.Bitmap")

objPortrait.LoadFromFile Server.MapPath("portrait.jpg")
objBackground.LoadFromFile Server.MapPath("background.jpg")

objPortrait.Data.ConvertTo32bppArgb

' Second parameter is a tolerance. It specifies how close pixel should be to the target pixel.
' If tolerance = 0, only pixels which are exactly equal to the target one are transparentized.
' If tolerance is >0, algorithm also transparentizes pixels which are close to target color. 
' It allows to avoid aliasing on the edges of your portrait.  
objPortrait.Channels.Transparentize ColorWhite, 5

Dim x, y
x = 100
y = 300
objPortrait.DrawOnBitmap objBackground, x, y, , , , , , , CombineModeAlpha

objBackground.SaveToStream Response
objBackground.SaveToFile Server.MapPath("Result.jpg")
%>

<!-- METADATA TYPE="typelib" UUID="{3CE48541-DE7A-4909-9314-9D0ED0D1CA5A}"--> 
<%

'Declarations
Dim objBackground	' The background image. It will contain the result of merge.
Dim objBitmap		' The image you put on the background.
Dim objMask		' This bitmap will contain alpha channel

Dim strBackgroundFilename
Dim strBitmapFilename
Dim strMergedFilename

' Specify file names here
strBitmapFilename = Server.MapPath("FrontImage.jpg")
strBackgroundFilename = Server.MapPath("BackgroundImage.jpg")
strMergedFilename = Server.MapPath("Result.jpg")

' Create bitmaps
Set objBitmap = Server.CreateObject("GraphicsMill.Bitmap")
Set objBackground = Server.CreateObject("GraphicsMill.Bitmap")

' Load bitmaps
objBackground.LoadFromFile strBackgroundFilename
objBitmap.LoadFromFile strBitmapFilename
objBitmap.Data.ConvertTo32bppArgb

objBitmap.Channels.Transparentize ColorWhite, 2

Set objMask = objBitmap.Channels.Extract(3)

'objMask.ColorAdjustment.Contrast 50
'objMask.Effects.MaximumFilter 2
'objMask.Effects.MedianFilter 1

objMask.Effects.Blur 1

objBitmap.Channels.Replace objMask, 3

' Apply alpha blending
objBitmap.DrawOnBitmap objBackground, , , , , , , , , CombineModeAlpha

' Save the result
objBackground.SaveToFile strMergedFilename
objBackground.SaveToStream Response

' Cleanup
Set objMask = Nothing
Set objBitmap = Nothing
Set objBackground = Nothing
%>

' Playing with brightness to remove unnecessary tone levels.
objMask.Brightness -254
objMask.Brightness 126

'Increase contrast to maximum
objMask.ColorAdjustment.Contrast 100

'It makes edges more smooth and fixes transparent teeth.
objMask.Effects.MedianFilter 3

Dim backgroundColor
backgroundColor = objBitmap.Data.Pixels(0,0) 
' Use this background in Transparentize...

' For brevity we will use Color class included into Graphics Mill
' Faster way would be to handle numeric values (decompose Long value 
' containing RGB triad into Bytes containing individual channels), but for 6 pixels
' we won't get noticeable effect.
Dim pixels(6) As color

' ...
' Let's assume you filled this array with appropriate pixels
' and ensured that you can treat them as background.
' Now we compose new Color value.

' Declare components as Long values. 
' We do not use Byte to avoid overflow, but 
' final value will contain number in range [0, 255]
Dim lngRed As Long
Dim lngGreen As Long
Dim lngBlue As Long 

' Do not forget to initialize these values!
lngRed = 0 
lngGreen = 0
lngBlue = 0

' Calculate per-channel sum
Dim I As Long
For I = LBound(pixels) To UBound(pixels)
   lngRed = lngRed + pixels(I).GetRed
   lngGreen = lngGreen + pixels(I).GetGreen
   lngBlue = lngBlue + pixels(I).GetBlue
Next I

' Find number of elements of array to divide 
Dim count As Long
count = UBound(pixels) - LBound(pixels) + 1

' objAverage - object which will construct the numeric value 
' (stored in lngAverage)
Dim objAverage As New Color
Dim lngAverage As Long 
lngAverage = objAverage.CreateRgb (lngRed/count, lngGreen/count, lngBlue/count)

' Use lngAverage as a background in next operations.