What is the meaning of this error (Using function medfilt2)

Hi I am using medfilt2 function but the error below is generated. May I know what is the problem here ?

TIA

---------------------------
I = imread('Moon.jpg');
J = imnoise(I, 'salt & pepper', 0.15);
L = medfilt2(J, [3 3]);
subplot(1,3,1); imshow(I); title('input image')
subplot(1,3,2); imshow(J); title('noisy image')
subplot(1,3,3); imshow(L); title('noisy image')
??? Error using ==> iptcheckinput
Function ORDFILT2 expected its first input, A, to be
two-dimensional.

Error in ==> ordfilt2>ParseInputs at 135
  iptcheckinput(A, {'numeric','logical'},
  {'2d','real'}, mfilename, 'A', 1);

Error in ==> ordfilt2 at 51
[A,order,domain,s,padopt,msg] =
ParseInputs(varargin{:});

Error in ==> medfilt2 at 53
    b = ordfilt2(a, order, domain, padopt);

Answer 1

[Wayne King]

You're likely trying to input a RGB image (3-D) to medfilt2. If you enter

size(J)

what is returned?

If the last number is 3, then that is a RGB image.

You can use rgb2gray to turn J into a 2-D matrix suitable for medfilt2

Answer 2

[Image Analyst]

When I use standard demo image moon.tif (which is grayscale) instead of moon.jpg, it works fine. Try your demo with that standard image - it's probably using some image you go that was saved as RGB. By the way, your last title should read

title('Denoised Image')

Answer 3

[Ramzan Shahid khan]

image J is in RGB of 3-D matrix but medfit2 takes 2-D. So first convert the J image into 2-D with rgb2gray(J) function, then it will work fine.