Algorithm 1. Word abstraction function α_w(in).

Input: an input in

Output: a word w

1: inI = αv(in)

2: w = ε, ri = 0

3: while ri + oRow < iRow do

4:   ci = 0

5:   while ci + oCol < iCol do

6:     w = w + αsS (inI [ri : ri + oRow][ci : ci + oCol]))

7:     ci = ci + oCol

8:   end while

9:   ri = ri + oRow

10: end while

11: return w