Figure 5 Examples of enlarging an image by replication and interpolation — replication simply copies the pixels and interpolation smooths the transitions

Input Image  Replication 2X  Interpolation 2X
   1  4         1 1 4 4          1 2 4 4
   6  9         1 1 4 4          3 5 6 6
                6 6 9 9          6 7 9 9
                6 6 9 9          6 7 9 9