Algorithm 1 Obtain the decrypted image P.

Decryptimg P = De_Img(Sr, SG, Sb, F′)

1: w = 0;

2: for i from 1 to 256

3:   for j from 1 to 256

4:   [r1, c1] ← find(F′ = w);

5:   d_r(i, j) ← Sr(r1, c1);

6:   d_g(i, j) ← Sg(r1, c1);

7:   d_b(i, j) ← Sb(r1, c1);

8:   w + 1 ← w;

9:  end

10: end

11: P ← d_r, d_g, d_b //Merge three channels