2D convolution in in Matlab.

I = imread ("lena.jpg");
%imshow(I);
K = I;
C = conv2(I, K);
imshow(C);

I am expecting something like the following as indicated in this link .

But, my output is blank:

What could be the possible reason?

And, how can I obtain the expected output?

Answer 1

[Guillaume]

What could be the possible reason? And, how can I obtain the expected output?

imshow expects that that intensity of a double image is in the range [0-1]. By default, anything less than 0 is displayed as black, and anything more than 1 is displayed as 1.

You can override that behaviour by passing a different range as the 2nd input to imshow or letting imshow use the intensity range of your image by passing []. So:

imshow(C, [])

should fix your problem.

Answer 2

[Matt J]

   I = im2double(  rgb2gray(  imread("lena.jpg") )  );

[Ba Ba Black Sheep!]

doesn't work.