Sample.bas

Function alpha22( ByVal source_pixel As ulong, ByVal destination_pixel As ulong, ByVal parameter As Any Ptr ) As ulong

	dim as ulong rgba1,rgba2,rgba3
	dim as ulong r1,g1,b1,a1
	dim as ulong r2,g2,b2,a2
	dim as ulong r3,g3,b3,a3

	/'
	Dim threshold As ulong = &HFF
	select case parameter
	case 0
	case else
	threshold = *CPtr(ULong Ptr, parameter)
	end select
	'/

	rgba1=source_pixel
	rgba2=destination_pixel

	a1=(rgba1 shr 24) and &HFF
	a2=(rgba2 shr 24) and &HFF

	r1=(rgba1 shr 16) and &HFF
	r2=(rgba2 shr 16) and &HFF

	g1=(rgba1 shr 8) and &HFF
	g2=(rgba2 shr 8) and &HFF

	b1=rgba1 and &HFF
	b2=rgba2 and &HFF

	r3=(r1 * a1 + r2 * a2) / &HFF / 2
	g3=(g1 * a1 + g2 * a2) / &HFF / 2
	b3=(b1 * a1 + b2 * a2) / &HFF / 2
	a3=(a1 + a2) / 2

	rgba3=rgba(r3,g3,b3,a3)

	function = rgba3
	exit function

end function