Error using medfilt2 Expected input number 1, A, to be two-dimensional.

I have an error using medfilt2, I don't know how to fix it. Please help, here I am using Matlab version R2020a.

Error starting from line 3. Here are the details of the error that appears when running :

1. Error using medfilt2. Expected input number 1, A, to be two-dimensional.
2. Error in medfilt2>parse_inputs (line 107). validateattributes(a, ...
3. Error in medfilt2 (line 49). [a, mn, padopt] = parse_inputs(args{:});

I=imread('peppers.png');
IN=imnoise(I,'salt & pepper',0.02);
J1=medfilt2(IN,[3 3]);
J2=medfilt2(IN,[5 5]);
figure,imshow(I);
figure,imshow(IN);
figure,imshow(J1);
figure,imshow(J2);

-Thank you in advance

Answer 1

[Walter Roberson]

peppers png is a color image. rgb images are 3D arrays. medfilt2 cannot process 3D arrays.

[Bara]

how to handle it? do you have a two-dimensional image?

I still don't understand what kind of image to use

[Walter Roberson]

Your next step is imnoise, and that says... https://www.mathworks.com/help/images/ref/imnoise.html#d123e157610 that the input image for it must be grayscale.

So you have several choices:

• convert the RGB image to grayscale and process the one plane
• process the three color planes independently and combine the result
• use medfilt3() instead of medfilt2() (this is probably not a good idea!)
• convert the RGB image to some other color systems such as L*ab or HSV, and extract one of the representation panes and work with that

For example,

I = imread('peppers.png');

HSV = rgb2hsv(I);
imshow(HSV); title('true hsv');

H = HSV(:,:,1);
H11 = H; H11(:,:,2:3) = 1;
imshow(H11); title('hsv with full S & V')

I11 = hsv2rgb(H11);
imshow(I11); title('RGB reconstructed from H + full S & V')

IN = imnoise(H,'salt & pepper',0.02);
J1 = medfilt2(IN, [3 3]);
HSV1 = J1; HSV1(:,:,2:3) = 1;
imshow(HSV1); title('noised H with full S & V')

I1 = hsv2rgb(HSV1);

imshow(I1); title('RGB reconstructed from noised H + full S & V')

imshowpair(I11, I1, 'diff')
title('no noise vs noise')

Answer 2

[Image Analyst]

See my attached salt and pepper noise demos.