Gaussian Filter without using any special function

Hi,

i need to apply a gaussian filter to the image without using imgaussfilt() function,

i create a gaussian mask:

[ 1, 4, 7, 4, 1; 
    4, 20, 33, 20, 4; 
    7, 33, 55, 33, 7; 
    4, 20, 33, 20, 4; 
    1, 4, 7, 4, 1 ] 

then i applied to the image and i get gaussian filtered image but i don't know to change the gaussian filter degree (sigma is 1 and i couldn't change this value),

so how can i use this mask with different sigma values.

Answer 1

[DGM]

Here is one example.

% specify input parameter as a scalar or 2-element vector
sigma = [4 5]; % [y x]

% expand if necessary
if isscalar(sigma); sigma = [1 1]*sigma; end

% generate kernel
r = ceil(2.5*sigma); % filter size is (2*r + 1) pixels
[xx yy] = meshgrid(-r(2):r(2),-r(1):r(1));
fk = exp(-(xx.^2/(2*sigma(2)^2) + yy.^2/(2*sigma(1)^2)));
fk = fk./sum(fk(:)); % sum-normalize

imshow(fk,[])