Zig-Zag Based Single-Pass Connected Components Analysis

. 2019 Apr 6;5(4):45. doi: 10.3390/jimaging5040045

Algorithm 2 UpdateNeighbourhood

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if $L_{B}^{-}$ then ▹ Select $L_{A o r D}$ based on whether A (previous B) is an object pixel
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$L_{A o r D} : = L_{B}^{-}$ ▹ Next value of $L_{A}$
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else
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$L_{A o r D} : = L_{X}^{-}$ ▹ Next value of $L_{D}$
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end if
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$L_{B} : = L_{C}^{-}$
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$L_{R B} : = R B [C]$ ▹ Look up position C in the row buffer
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if $L_{R B}$ then ▹ An object pixel is coming into neighbourhood
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if $\neg L_{C}^{-}$ then ▹ It is the first object pixel after a background pixel
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$L_{M T} : = M T [L_{R B}]$ ▹ First lookup in merger table
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if $L_{M T} = L_{R B}$ then ▹ Label was representative label
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$L_{C} : = L_{M T}$
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else
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$L_{C} : = M T [L_{M T}]$ ▹ Second lookup in merger table to get representative label
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if $L_{C} \neq L_{M T}$ then ▹ Label change on second lookup indicates a chain
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$M T [L_{R B}] : = L_{C}$ ▹ Update merger table to unlink the chain
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end if
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end if
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else ▹ Part of a run of consecutive pixels
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$L_{C} : = L_{C}^{-}$ ▹ Repeat latest label
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if $L_{R B} \neq L_{R B}^{-}$ then ▹ Label has changed, indicating a chain of mergers
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$M T [L_{R B}] : = L_{C}$ ▹ Update merger table to unlink the chain
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end if
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end if
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else
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$L_{C} : = 0$ ▹ Lookup of background is unnecessary
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end if