A Computational Introduction to Digital Image Processing, 2nd Edition

464 A Computational Introduction to Digital Image Processing, Second Edition

MATLAB/Octave

>> x=1:12;

>> x+mod(x,4)

ans

=

2 4 6 4 6 8 10 8 10 12 14 12

or

Python

In : x = np.array(range(1,13))

In : print np.vstack((x,x+x%4))

[[ 1 2 3 4 5 6 7 8 9 10 11 12]

[ 2 4 6 4 6 8 10 8 10 12 14 12]]

Notice that although the values increase from left to right, they do in small runs, which

seem to overlap. On an image, the appearance will be of a ripple across the image. We

shall experiment first using Cartesian coordinates:

MATLAB/Octave

>> [y,x] = meshgrid(1:cols,1:rows);

>> y2 = y+mod(y,32);

>> y2 = clip(y2,1,cols);

Here we have just added moduli across the columns, then