Currently I am trying to convolve an image with a Gaussian function and am getting a white screen.

When I am trying to get the convolution I am getting blank screen. The code I have for this is given by:

p = imread('barphantom.png');
gp = rgb2gray(p)
figure, imshow(p) %shows the image
n = 1132;
m = 755;

sigma = 5 

h = zeros(n,m);

for x=1:n
    for y=1:m
        h(x,y) = exp(-((x-n/2)^2+(y-m/2)^2)/(2*sigma^2));  
    end
end

figure, imshow(h) % shows the gaussian figure

k = conv2(gp, h,'same')
figure, imshow(k)

Answer 1

[DGM]

Sum-normalize the filter kernel

gp = imread('cameraman.tif');

n = 1132;
m = 755;
sigma = 5;
h = zeros(n,m);
for x=1:n
    for y=1:m
        h(x,y) = exp(-((x-n/2)^2+(y-m/2)^2)/(2*sigma^2));
    end
end
h = h/sum(h(:)); % normalize the filter

%imshow(h) % shows the gaussian figure
k = conv2(im2double(gp), h,'same');
imshow(k)

Your filter also is wayyyy bigger than it needs to be. That only slows down the convolution. Depending on how much support you want, you can make it quite small. For comparison, imgaussfilt() creates the filter such that its width and height are 2*ceil(2*sigma)+1. You might want more support, so pick 2*ceil(3*sigma)+1 or 2*ceil(4*sigma)+1.

[Levi Stevens]

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