having problem with error "index out of bounds" numel (Y)=1"

Hello all! I am trying to write a code that takes the noise out of bitmap images, and re-writes them as a cleaned image afterward. I'm not done with the code entirely yet, but my function file keeps spitting out the error

Attempted to access Y(8,1); index out of bounds because numel(Y)=1.
Error in fixp (line 13)
  A = [(Y((i-1), j)),(Y((i-1),(j+1))),(Y(i,(j+1))),(Y((i+1),j)),(Y((i+1),(j+1)))];

Here is what my main file looks like:

    clc;
clear;
format compact;
% Image importing
A = imread('J20_pic1_noisy.bmp');
[m,n,p] = size(A);
for k = [1:p];
    for j = [1:n];
        for i = [1:m];
             Y = A(i,j,k);
                if Y == 0 | Y == 255; 
                [B] = fixp(Y,i,j,m,n);
                end

        end
    end
end

and here is what the function file looks like:

    function[B] = fixp(Y,i,j,m,n);
B = [];
if i == 1 & j == 1 % top left corner 
    A = [(Y(i, j+1)),(Y(i+1,j)),(Y(i+1,j+1))];
    B(i, j)= mean(median(A));
elseif i == 1 & j > 1 & j < n %top side
    A = [(Y(i, j-1)),(Y(i,j+1)),(Y(i+1,j-1)),(Y(i+1,j)),(Y(i+1,j+1))];
    B(i, j)= mean(median(A));
elseif i == 1 & j == n % top right corner
    A = [(Y(i, j-1)),(Y(i+1,j-1)),(Y(i+1,j))];
    B(i, j)= mean(median(A));
elseif i > 1 & i < m & j == 1 % left side
    A = [(Y(i-1, j)),(Y(i-1,j+1)),(Y(i,j+1)),(Y(i+1,j)),(Y(i+1,j+1))];
    B(i, j)= mean(median(A));
elseif i > 1 & i < m & j == n % right side
    A = [(Y(i-1, j-1)),(Y(i-1,j)),(Y(i,j-1)),(Y(i+1,j-1)),(Y(i+1,j))];
    B(i, j)= mean(median(A));
elseif i == m & j == 1 %bottom left corner
    A = [(Y(i-1, j)),(Y(i-1,j+1)),(Y(i,j+1))];
    B(i, j)= mean(median(A));
elseif i == m & j > 1 & j < n %bottom side
    A = [(Y(i-1, j-1)),(Y(i-1,j)),(Y(i-1,j+1)),(Y(i,j-1)),(Y(i,j+1))];
    B(i, j)= mean(median(A));
elseif i == m & j == n %bottom right corner
    A = [(Y(i-1, j-1)),(Y(i-1,j)),(Y(i,j-1))];
    B(i, j)= mean(median(A));
elseif i > 1 & i < m & j > 1 & j < n %every other position
   A = [(Y(i-1, j-1)),(Y(i-1,j)),(Y(i-1,j+1)),(Y(i,j-1)),(Y(i,j+1)),(Y(i,j-1)),(Y(i,j+1)),(Y(i+1,j-1)),(Y(i+1,j)),(Y(i+1,j+1))];
    B(i, j)= mean(median(A));
end
end

Does anyone know what is causing the error, and subsequently, how to fix it? Thank you!

[Joey]

Hey all, I ended up getting the script to do what I needed to do. Here is my final result (that works).

    clc;
clear;
format compact;
% Image importing
fname = uigetfile('.bmp','Pick the file');
A = imread(fname);
[m,n,p] = size(A);
B = A; 
figure(1)
image(A)
for k = [1:p];
    for j = [1:n];
        for i = [1:m];
          Y = B(i,j,k);
            if Y == 0 | Y == 255; 

                if i == 1 & j == 1; % top left corner 
                        Z = [(B(i, j+1)),(B(i+1,j)),(B(i+1,j+1))];
                        B(i,j,k) = median(Z);

                elseif i == 1 & j > 1 & j < n; %top side
                        Z = [(B(i, j-1)),(B(i,j+1)),(B(i+1,j-1)),(B(i+1,j)),(B(i+1,j+1))];
                        B(i,j,k) = median(Z);

                elseif i == 1 & j == n; % top right corner
                        Z = [(B(i, j-1)),(B(i+1,j-1)),(B(i+1,j))];
                        B(i,j,k) = median(Z);

                elseif i > 1 & i < m & j == 1; % left side
                        Z = [(B(i-1, j)),(B(i-1,j+1)),(B(i,j+1)),(B(i+1,j)),(B(i+1,j+1))];
                        B(i,j,k) = median(Z);

                elseif i > 1 & i < m & j == n; % right side
                        Z = [(B(i-1, j-1)),(B(i-1,j)),(B(i,j-1)),(B(i+1,j-1)),(B(i+1,j))];
                        B(i,j,k) = median(Z);

                elseif i == m & j == 1; %bottom left corner
                        Z = [(B(i-1, j)),(B(i-1,j+1)),(B(i,j+1))];
                        B(i,j,k) = median(Z);

                elseif i == m & j > 1 & j < n; %bottom side
                        Z = [(B(i-1, j-1)),(B(i-1,j)),(B(i-1,j+1)),(B(i,j-1)),(B(i,j+1))];
                        B(i,j,k) = median(Z);

                elseif i == m & j == n; %bottom right corner
                        Z = [(B(i-1, j-1)),(B(i-1,j)),(B(i,j-1))];
                        B(i,j,k) = median(Z);

                elseif i > 1 & i < m & j > 1 & j < n; %every other position
                        Z = [(B(i-1, j-1)),(B(i-1,j)),(B(i-1,j+1)),(B(i,j-1)),(B(i,j+1)),(B(i,j-1)),(B(i,j+1)),(B(i+1,j-1)),(B(i+1,j)),(B(i+1,j+1))];
                        B(i,j,k) = median(Z);

                end
            end
        end
    end
end
figure(2)
image(B)
fnameo = uiputfile('.bmp','Insert desired output filename');
imwrite(B,fnameo);

Answer 1

[Image Analyst]

You're going overall rows and all columns but trying to access a 3x3 window around it. What will happen if you are at the edge of an image? You'd have i or j = -1. There is no -1 row. Try going from i = 1:rows, and j = 2:columns.

[Joey]

Okay. What then, about how I have 9 separate elseif loops for the different possible locations of Y? Would I only have 1 condition, instead of 9? Thank you.

[Image Analyst]

No, that's not good. What are you trying to do anyway? What kind of weird filter is it that does median across columns and then averages them? I've never heard of that. Why not just do a 2D median filter? Why not use medfilt2()?

[Joey]

Thanks, I had never seen this function before. I'm in an entry level matlab class, and we're supposed to be using loops to accomplish the image cleaning. We're given both a black and white and a color image with "salt and pepper" noise and tasked with removing the noise and creating an image without the noise. When you say to use i=1:rows and j=2:columns, where should I enter that? I apologize, I am very new to matlab and this is the first project I have ever done with it, so I am not great with syntax yet.

[Image Analyst]

See attached demos for salt and pepper noise removal.

Answer 2

[Iain]

The error is actually quite clear:

Before calling the fixp function, you're setting "Y" to be a scalar.

Inside the fixp function, you're treating Y, as if it is a 3x3 matrix.

If you put

 Y = A(:,:,k), then it should work.