Comunque si basa tutto su
For x as integer = 0 to (bitmap1.weight + bitmap2.weight)-1
For y as integer = 0 to (bitmap1.height + bitmap2.height)-1
If bitmap1.getpixel(x,y).equals(bitmap2.getpixel(x,y)) that
Bitmap3.setpixel(x,y,color)
Else
Bitmap3.setpixel(x,y, color)
End if
Next y
Next x