I would like to scramble image using henon map.I have written the following code with the help of bifurcation diagram matlab code.

if true
  % code
clc;
clear all;
close all;
imag1= imread('desert.jpg');
%info = imfinfo('barbara.jpg');
%if((info.ColorType)~='gray scale')
v=rgb2gray(imag1);
subplot(1,2,1);
[rows, columns] = size(v);
N=rows;
M=columns;
imshow(imag1);
x(1)=0;
y(1)=0;
[height, width] = size(v);
i=2;
for i=2:10000
  x(i)=mod(1-1.4*(x(i-1)^2)+y(i-1),N)+1;
  y(i)=mod(0.3*x(i-1),N)+1;
  m=x(i);
  n=y(i);
  for r=1:M
      for c=1:N
          v1(r,c)=v(m,n);
      end
  end
end

    v2 = im2uint8(v1);
    subplot(1,2,2);
    imshow(v2);

    results = NPCR_and_UACI(v,v2);
  end

I am getting error due to modulus statement.

after applying mod..there should be integer value...

But We're getting fractional part.How?Can anyone explain this?