image zooming using cross pixel interpolation

an NxM image is zoomed in using cross pixel interpolation algorithm

% Cross Pixel Interpolation Zooming
% function pf=xpixelzoom(x,k)
% x is the input N-by-M original image. It is not a condition that N=M.
% pf is the output zoomed image.
% k is the doubling factor. That is the original image is doubled in size
% k times. Actually, an NxM image is zoomed to a 2N+1x2M+1 larger image.
% For more details, contact me at [e-mail]