Drawing one image onto another

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Jur

I am using the following function to combine several layers of tiles into one tile.


Function MakeBlendedImage:TImage(Image:TImage[])
	If image.length=Null Then Return
	Local Pixmap:TPixmap=CopyPixmap(image[0].pixmaps[0])
	
	Local R1,G1,B1,A1	'overlaying image  	
	Local R2,G2,B2,A2	'background image 
	Local finalAlpha#	
	For Local i=1 Until image.length
		If image[i]=Null Then Continue
		For Local x=0 Until pixmap.width
			For Local y=0 Until pixmap.height
				GetRGBAfromColorValue(ReadPixel(pixmap,x,y),R2,G2,B2,A2)
				GetRGBAfromColorValue(ReadPixel(image[i].pixmaps[0],x,y),R1,G1,B1,A1)
				finalAlpha=GetFinalAlpha(A1,A2)
				WritePixel(Pixmap,x,y, GetColorValueFromRGBA(GetFinalColor(R1,A1,R2,A2, finalAlpha), GetFinalColor(G1,A1,G2,A2,finalAlpha), GetFinalColor(B1,A1,B2,A2,finalAlpha),finalAlpha))
			Next
		Next
	Next
	
	Function GetFinalColor(color1,alpha1, color2,alpha2,  finalAlpha#)
		Return (alpha1*color1/finalAlpha + alpha2*color2*(255-alpha1)/finalAlpha/255.0)
	EndFunction
	
	Function GetFinalAlpha:Float(alpha1,alpha2)
		Return (255-(255-alpha1)*(255-alpha2)/255.0)
	EndFunction

	Return LoadImage(Pixmap)
EndFunction

The first index of image array is the bottom layer. All images must be of the same size. For images with diferent sizes, the read-write pixel loop should be changed.

Jure