[polopok]

Для тех ,кто привык задавать значения от 0.0 до 1.0

Function AlphaRect(Point_X# = 0 ,Point_Y# = 0 ,width ,height ,R = 255 ,G = 255 ,B = 255 ,A# = 1.0 ,border = False)

If A <= 0 And border = False
    Return
ElseIf (A <= 0 And border = True ) Or (A > 0 And border = False ) Or (A > 0 And border = True )

    Buffer = BackBuffer()
    LockBuffer Buffer
    RGB =  255 Shl 24 Or R Shl 16 Or G Shl 8 Or B ;
    For localY# = Point_Y To  Point_Y + height -1
    For localX# = Point_X To Point_X + width -1
        If localX > 0 And localX < GraphicsWidth() And localY > 0 And localY < GraphicsHeight()
        bgRGB = ReadPixelFast (localX ,localY ,Buffer )

        WritePixelFast localX ,localY , GetPixelForOpacity( bgRGB , RGB , A),Buffer
        
        If border
            NewRGB =(1.0-RGB *(A-((1.0-RGB )*(1.0-bgRGB  ) Shr 8)-A) Shr 8)
            WritePixelFast localX ,Point_Y , NewRGB ,Buffer
            WritePixelFast localX ,Point_Y+ height , NewRGB , Buffer
            WritePixelFast Point_X ,localY, NewRGB ,Buffer
            WritePixelFast Point_X + width ,localY, NewRGB , Buffer
        EndIf
        End If

    Next : Next
    UnlockBuffer Buffer
End If
End Function 

Function GetPixelForOpacity( pixelBackground, pixelForeground, pixelAlpha#)
    If pixelForeground = $ff000000 Then pixelForeground = pixelBackground
        bgsourceR = ((pixelForeground And $00FF0000) Shr 16);
        bgsourceG = ((pixelForeground And $0000FF00) Shr 8);
        bgsourceB = ((pixelForeground And $000000FF));

        sourceR = ((pixelBackground And $00FF0000) Shr 16);
        sourceG = ((pixelBackground And $0000FF00) Shr 8);
        sourceB = ((pixelBackground And $000000FF));

        newR = sourceR * pixelAlpha/1.0 + bgsourceR * ( 1.0-pixelAlpha)/1.0;
        newG = sourceG * pixelAlpha/1.0+ bgsourceG * (1.0- pixelAlpha)/1.0;
        newB = sourceB * pixelAlpha/1.0+ bgsourceB * (1.0- pixelAlpha)/1.0;

        Return (255 Shl 24 Or newR Shl 16 Or newG Shl 8 Or newB);
End Function