Code archives/Graphics/AlphaBlit

Dim pixelData(500, 500)
Function AlphaBitBlit(DestBuffer, Image, xOff, yOff, Alpha#)
	;This function alpha blits any image smaller than 100,50 onto a desitantion
	;buffer of equal or lesser size, It has no error handling to speed up the 
	;function.
	
	;DestBuffer is the pointer to the desitnation image.
	;ImgBuffer is the pointer to the image to be Alpha Blited.
	;xOff, yOff are the ofsets of the image on the destination image.
	;Alpha ranges from 0 to 1 and is the opacity of the image.

	InvAlpha# 	= 1.0 - Alpha#
	ImgBuffer 	= ImageBuffer(Image)
	iWidth 		= ImageWidth(Image)
	iHeight 	= ImageHeight(Image)
	
	LockBuffer ImgBuffer
		For x = 0 To iWidth-1
			For y = 0 To iHeight-1
				pixelData(x, y) = ReadPixelFast(x,y,ImgBuffer)
			Next
		Next
	UnlockBuffer ImgBuffer
	LockBuffer DestBuffer
		For x = 0 To iWidth-1
			For y = 0 To iHeight-1
				PixA# = ReadPixelFast(x + xOff, y + yOff)
				PixB# = pixelData(x, y)
				
				;Calculate Alphas with the least number of computations
				aR = Int(PixA Sar 16)
				aRI = aR Shl 16
				aG = Int((PixA - aRI) Sar 8)
				aB = PixA - (aRI + (aG Shl 8))

				;Calculate Alphas with the least number of computations
				bR = Int(PixB Sar 16)
				bRI = bR Shl 16
				bG = Int((PixB - bRI) Sar 8)
				bB = PixB - (bRI + (bG Shl 8))
				
				;Apply Alphas
				If bR > 0 Or bG > 0 Or bB > 0
					nR = (aR * InvAlpha) + (bR * Alpha)
					nG = (aG * InvAlpha) + (bG * Alpha)
					nB = (aB * InvAlpha) + (bB * Alpha)
				
					;Write Pixel to Buffer
					WritePixelFast x + xOff, y + yOff, (nR Shl 16) + (nG Shl 8) + nB
				EndIf
			Next
		Next
	UnlockBuffer DestBuffer
End Function