I have this filtering function that takes an input image, performs convolution using a given kernel, and returns the resulting image. However, I can't seem to work it out how to make it takes different kernel sizes.For example instead of pre-defined 3x3 kernel as below in the code, it could instead take 5x5 or 7x7. and then the user could input the type of kernel/filter they want(Depending on the intended effect). I can't seem to put my head around it. i'm quite new to matlab.
function [newImg] = kernelFunc(imgB)
img=imread(imgB);
figure,imshow(img); 
img2=zeros(size(img)+2);
newImg=zeros(size(img));
for rgb=1:3
        for x=1:size(img,1)
            for y=1:size(img,2)
                img2(x+1,y+1,rgb)=img(x,y,rgb);
            end
        end
end
for rgb=1:3
    for i= 1:size(img2,1)-2
        for j=1:size(img2,2)-2
            window=zeros(9,1);
            inc=1;
            for x=1:3
                for y=1:3
                    window(inc)=img2(i+x-1,j+y-1,rgb);
                    inc=inc+1;
                end
            end
           kernel=[1;2;1;2;4;2;1;2;1]/16;
            med=window.*kernel;
            disp(med);
            med=sum(med);
            med=floor(med);
            newImg(i,j,rgb)=med;
        end
    end
end
newImg=uint8(newImg);
figure,imshow(newImg);
end