Mysterious face appears after applying filter

I am applying a median filter to a noisy image and them subplot them for comparison. It works fine, except that there's a dark block on the top left corner of my image. When I zoom in further, I see a face of a boy.

Here's an uploaded screenshot and the zoomed image:

http://img153.imageshack.us/i/problem01.jpg/

http://img232.imageshack.us/i/problem02.jpg/

Is this some Halloween prank? Has anyone encountered this? How can I remove it?

Here's my code:

dirty = importdata('dirtytabur.jpg');

if size(dirty,3) == 3
    dirty = rgb2gray(dirty);
end

filtered = medfilt2(dirty);

% display image
scrsz = get(0, 'ScreenSize');
figure('Position', [1 1 scrsz(3) scrsz(4)]);

subplot(1,2,1); 
imshow(dirty);title('Before Processing'); axis equal;axis tight;

subplot(1,2,2); 
imshow(filtered);title('After Processing'); axis equal;axis tight;
% figure(filtered);

imwrite(image,[filename '.jpg'], 'jpg');

Thanks, Yu Ang

Answer 1

[Walter Roberson]

imwrite(filtered, [filename '.jpg'], 'jpg');

You used image instead of filtered, and image is the name of a function to display an image; when not told what array of data to display as an image, the default for image() is the face of a boy.

[Jiro Doke]

Here's a blog post about it (and more):

http://blogs.mathworks.com/steve/2006/10/17/the-story-behind-the-matlab-default-image/

Answer 2

[Yu Ang Tan]

Thank you very much.

This code is originally part of a function, which takes in a parameter 'image'. I was careless for not noticing that 'image' is an built-in function.