performing without randperm function

from code below i get 10 matrix values,using randperm function,please can anyone tell how to perform without using randperm,

A=imread('dock.jpg');
A=rgb2gray(A);
A=imresize(A,[256 256])
A=double(A)
n = numel(A);
A1_10 = repmat(A,[1,1,10]);
t = ones(size(A));
for j1 = 1:size(A1_10,3)
    p = t;
    k = randperm(n);
   k1=[1:n];
    p(k(1:6000)) = 0;
    A1_10(:,:,j1) = A1_10(:,:,j1).*p;
end
A1_10

[FIR]

Walter may i know what u have edited

Answer 1

[Andrei Bobrov]

A=imread('dock.jpg');
A=rgb2gray(A);
A=imresize(A,[256 256])
A=double(A)
n = numel(A);
A1_10 = repmat(A,[1,1,10]);
t = ones(size(A));
for j1 = 1:size(A1_10,3)
    p = t;
    p(randi(n,6000,1)) = 0;
    A1_10(:,:,j1) = A1_10(:,:,j1).*p;
end
A1_10

[FIR]

Thanks andrei