The modified pixel color is calculated by subtracting the level of {HEAD ~ gray} in the original pixel color from each of the three original component color values and increasing any remaining color component values as {TAIL ~ a function} of the modified alpha value of the pixel 
The modified pixel color is calculated by subtracting the level of { HEAD ~ gray } in the original pixel color from each of the three original component color values and increasing any remaining color component values as { TAIL ~ a function } of the modified alpha value of the pixel
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH