From Directorforum Collaboration Wiki
--result := a AND b;
-- ******* AND mode *************
on ANDBlendMode (image1, image2)
theWidth = image1.width - 1
theHeight = image1.height - 1
theImage = image(theWidth + 1, theHeight + 1, 32)
repeat with x = 0 to theWidth
repeat with y = 0 to theHeight
theColour1 = image1.getPixel(point(x,y), #integer)
theColour2 = image2.getPixel(point(x,y), #integer)
theNewColour = bitAnd(theColour1, theColour2)
theImage.setPixel(point(x, y), theNewColour)
end repeat
end repeat
return theImage
end