Composite Images with Alpha

 

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This behavior composites multiple image objects with alpha but does not suffer from the common problem of the images getting ragged or muddled alphas in the process.

--Copyright 2004-2005 --Chuck Neal --MediaMacros, Inc. --Enjoy ;) on compositeImage vImage, vDestImage, vDestRect, vSourceRect, vBackColor   if vBackCOlor = void then vBackColor = rgb(0,0,0)   iDestImage = vDestImage.duplicate()      --Fill with a solid back color   iDestImage.fill(iDestImage.rect, vBackCOlor)      iSourceImage = vImage.duplicate()      -- get the original alpha channel   iAlphaBuffer = vDestImage.extractAlpha()      --get the composite alpha   if iSourceImage.depth = 32 then     iSourceAlphaBuffer = iSourceImage.extractALpha()   else     --create a new super image alpha     iSourceAlphaBuffer = image(iSourceImage.width, iSourceImage.height, 8, #grayscale)     iSourceAlphaBuffer.fill(iSourceAlphaBuffer.rect, rgb(0,0,0))       end if      --Disable both alphas for the copy pricess   vDestImage.useAlpha = FALSE   iSourceImage.useAlpha = FALSE            iDestMask = iAlphaBuffer.createMask()   iDestImage.copyPixels(vDestImage, vDestImage.rect, vDestImage.rect, [#maskimage : iDestMask, #ink : #add, #dither : 1969])      iSourceMask = iSourceImage.extractalpha().createMask()   iDestImage.copyPixels(iSourceImage, vDestRect, vSourceRect, [#maskimage : iSourceMask, #dither : 1969])      --reverse dark to light   iAlphaReverse = image(iSourceImage.width, iSourceImage.height, 8, #grayscale)   --alphatoAdd.duplicate()   iAlphaReverse.fill(iAlphaReverse.rect, rgb(0,0,0))   iAlphaReverse.copyPixels(iSourceAlphaBuffer, iAlphaReverse.rect, iSourceAlphaBuffer.rect, [#ink : #reverse])      iALphaBuffer.copyPixels(iAlphaReverse, vDestRect, vSourceRect, [#ink:#subtractpin])      -- apply the alpha changes   iDestImage.setAlpha(iALphaBuffer)     iDestImage.useAlpha = TRUE       return iDestImage end