Algorithm 2. ColorStep algorithm

Inputs: mapColor, mapData, clusterN, point, color; eps, s

Outputs: mapColor

i ← point.i

j ← point.j

e ← mapData.mainDirection(i, j)

e → direction: {[0, 1]; [1, 0]; [1, 1]; [−1, 1]}

tangent ← map(direction): {[1, 0]; [0, 1]; [−1, 1]; [1, 1]}

diag ← map(direction): {[1, 1] and [−1, 1]; [1, 0] and [0, 1]}

ptemp ← size (mapColor == s and mapData.cluster = color(clusterN))

ptemp ← ptemp/size(mapColor and mapData.cluster = color(clusterN))

β ← mapData.ellipticity(i, j)

p ← mapData. cluster(clusterN).meanPorosity

If |p(cluster) − ptemp|/ptemp > eps

break

end if

If mapColor [(i,j) ± direction] ≠ s and mapData.cluster = color(clusterN) then mapColor [(i,j) ± direction] += 1

else

colorStep(mapColor, (i,j) ± direction, β, e, s)

end if

If mapColor [(i,j) ± tangent] ≠ s and mapData.cluster = color(clusterN) then mapColor [(i,j) ± tangent] += β

else  break

colorStep(mapColor, (i,j) ± tangent, β, e, s)

end if

If mapColor [(i,j) ± diag] ≠ s and mapData.cluster = color(clusterN) then mapColor [(i,j) ± diag] += sqrt(2β2/(β2 + 1))

else

colorStep(mapColor, (i,j) ± diag, β, e, s)

end if