my code doesnt go into the loop

    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.......

[Jan]

The question would be much easier to understand, if yo omit all unnecessary details. Actually you need these two lines only:

[m n] = size (difference_red);

while ( i == 2:m-1 && j == 2:n-1 )

The rest is only confusing.

Answer 1

[Wayne King]

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

[prem preet]

its doesnt work sir ......

the code still dont go into the loop

[Jan]

@prem: Accepting an answer means, that your problem is solved. But you comment sounds, like there are still problems.

Please explain exactly, what you have changed.

Answer 2

[Jan]

[m, n] = size (difference_red);
while ( i == 2:m-1 && j == 2:n-1 )  % Not working

The argument of while contains vectors: "i == 2:m-1" is a LOGICAL vector. But the && operator works on scalars only. If you use the & or and() operation, the next problem occurs: Then the two logical vectors i==2:m-1 and j==2:n-1 must have the same number of elements or one must be a scalar, because the and works elementwise.

Assuming that both LOGICAL vectors have teh same size accidently, the next problem occurs: If the argument of while or if is not a scalar, a all is inserted automatically:

while all(i == 2:m-1 & j == 2:n-1)

But there is always an element, which is not true in the vector (if it can be evaluated at all, see above). Therefore I assume the two FOR loops suggested by Wayne are doing what your want.