a = numpy.array([[1, 5, 9], [2, 7, 3], [8, 4, 6]])
step = 0.5
xstop, ystop = a.shape
x = numpy.arange(0, xstop, step).astype(int)
y = numpy.arange(0, ystop, step).astype(int)
mg = numpy.meshgrid(x, y)
b = a[mg].T
b
Resizing and stretching a NumPy array