Index in position 1 is invalid. Array indices must be positive integers or logical values. i am getting this error for averaging filter

i=imread('Lena512.png');

[m n]=size(i)

mask=ones(3,3)/9;

in=zeros([m n]);

for k=1:1:m-1

for l=1:1:n-1

t=i(k-1,l-1)*mask(1,1)+i(k-1,l)*mask(1,2)+i(k-1,l+1)*mask(1,3)+i(k,l-1)*mask(2,1)+i(k,l)*mask(2,2)+i(k,l+1)*mask(2,3)+i(k+1,l-1)*mask(3,1)+i(k+1,l)*mask(3,2)+i(k+1,l+1)*mask(3,3)

in(k,l)=t

im2double(in)

end

end

imshow(k)

imshow(in)

Answer 1

[Kevin Holly]

i=imread('peppers.png');
[m n]=size(i)

m = 384

n = 1536

mask=ones(3,3)/9;
in=zeros([m n]);
for k=1:1:m-1
    for l=1:1:n-1
         t=i(k-1,l-1)*mask(1,1)+i(k-1,l)*mask(1,2)+i(k-1,l+1)*mask(1,3)+i(k,l-1)*mask(2,1)+i(k,l)*mask(2,2)+i(k,l+1)*mask(2,3)+i(k+1,l-1)*mask(3,1)+i(k+1,l)*mask(3,2)+i(k+1,l+1)*mask(3,3)
        in(k,l)=t
        im2double(in)
    end
end

Index in position 1 is invalid. Array indices must be positive integers or logical values.

The problem above occurs when

k = 1

and

l = 1

When looking at a specific index in the matrix i,

i(k-1,l-1)

you get

i(0,0)

which does not exist.

You could try:

for k=2:1:m-1
    for l=2:1:n-1
         t=i(k-1,l-1)*mask(1,1)+i(k-1,l)*mask(1,2)+i(k-1,l+1)*mask(1,3)+i(k,l-1)*mask(2,1)+i(k,l)*mask(2,2)+i(k,l+1)*mask(2,3)+i(k+1,l-1)*mask(3,1)+i(k+1,l)*mask(3,2)+i(k+1,l+1)*mask(3,3)
        in(k,l)=t
        im2double(in)
    end
end

[Rishith Reddy]

thank you