MATLAB: The code doesnt go into the loop

Image Processing Toolbox

    picture = imread ('C:\Users\prempreet\Desktop\lena512color.tiff');
    noisy_picture= imnoise (picture,'salt & pepper', 0.10)
    % image = picture(: , :);
    image_red = picture (:, :, 1);
    image_green = picture (:, :, 2);
    image_blue = picture (:, :, 3);
    redChannel = noisy_picture(:, :, 1);
    greenChannel = noisy_picture(:, :, 2);
    blueChannel = noisy_picture(:, :, 3);
    %median = medfilt2 ( image );
    red_median = medfilt2 (redChannel);
    blue_median = medfilt2 (blueChannel);
    green_median = medfilt2 (greenChannel);
    difference_red = abs (redChannel - red_median);
    difference_blue = abs (blueChannel - blue_median);
    difference_green = abs (greenChannel - green_median);
    difference_red = im2double (difference_red);
    difference_green = im2double (difference_green);
    difference_blue = im2double (difference_blue);
    [m n] = size (difference_red);
    while ( i == 2:m-1 && j == 2:n-1 )
    a1 = [difference_red(i-1,j-1), difference_red(i-1,j), difference_red(i-1,j+1), difference_red(i,j-1), difference_red(i,j), difference_red(i,j+1),difference_red(i+1,j-1), difference_red(i+1,j), difference_red(i+1,j+1)];
    b1 = [difference_blue(i-1,j-1), difference_blue(i-1,j), difference_blue(i-1,j+1), difference_blue(i,j-1), difference_blue(i,j), difference_blue(i,j+1), difference_blue(i+1,j-1), difference_blue(i+1,j), difference_blue(i+1,j+1)];
    c1 = [difference_green(i-1,j-1), difference_green(i-1,j), difference_green(i-1,j+1),difference_green(i,j-1), difference_green(i,j), difference_green(i,j+1), difference_green(i+1,j-1), difference_green(i+1,j), difference_green(i+1,j+1)];
    a2 = a1(a1<=0.7);
    b2 = b1 (b1<= 0.7);
    c2 = c1 (c1<=0.7);
    med_red (i,j)= median (a2);
    med_blue (i,j)= median (b2);
    med_green (i,j)= median (c2);
the code doesnt go into the loop…….

Best Answer

That is not correct syntax for a while loop. For example:
% This does not work!
n = 1;
while (n==1:4)
disp('Hi'); 
n = n+1;
end
   % This works!
   n = 1;
   while (n>=1 & n<4)
   disp('Hi'); 
   n=n+1;
   end
Without getting in the specifics of your code, how about trying:
for i=2:m-1
 for j = 2:n-1
...
...
end
end
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