Chamfer Mask:
( 1,  0,  0,  0,   3)
( 1,  1,  0,  0,   4)
( 1,  1,  1,  0,   5)
( 1,  1,  1,  1,   6)

Computed Lut Mask:
( 1,  0,  0,  0,   3)
( 1,  1,  0,  0,   4)
( 1,  1,  1,  0,   5)
( 1,  1,  1,  1,   6)

Look-Up Table: values which differ from LMC (L = 128, R <= 380)
Lut[][    3 ] =     4     5     6     7