Index in position 1 exceeds array bounds (must not exceed 1)

Howdy all, super novice here.

Im trying to write a program to reduce the noise on an image by clustering, that is I want to take the value of a single pixel, and if it and at least 3 of its neighbors in a 3x3 area (with the pixel in question at the center) have a value of 1, keep the value of the center pixel at one. otherwise, set the center pixel to 0. Also, i want it to perform this function for all pixels in a 232 X 251 image. One of the problems I'm running into is that I tried to take into account the corner/ border pixels so as not to exceed the array bounds, but i still get an error.

For image named "blackandwhite"

r = size(blackandwhite,1);
c = size(blackandwhite,2);
 
 
    for r = 2:1:max(r)-1
        for c = 2:1:max(c)-1
            if ((T(r,c)+T(r+1,c)+T(r-1,c)+T(r+1,c+1)+T(r,c+1)+T(r-1,c+1)+T(r+1,c-1)+T(r,c-1)+T(r-1,c-1)) < 3), T=0;
        
            end
        end
    end

Anybody have any advice as to how to proceed? Thanks in advance!

(please use small words, still not versed in the jargon of matlab)

Answer 1

[Walter Roberson]

The first time your if condition is true, you do T=0 which replaces all of T with the scalar 0. Then your loop continues and tries to index using sizes from the original T array, but T has been replaced with just the single 0. You should be assigning to T(r,c) instead of T.

Note: the way you use c = size(blackandwhite,2) and then for c = 2:1:max( c)-1 is confusing, because you are using c with two different meanings there. Also, size() with a dimension number always returns a scalar, so there is no need to look at max() of it.