how to black out part of an image ?

Hello all I have a question on how to black out part of my image. (the clown smile)

i have the code to load it all in.

But need to black out the smile of the image

im=imread(im=imread('scaryclown.png'); % loadimage; 
im=double(rgb2gray(im));% make double and gray scale.
subplot(211); %make a subplot
imagesc(im); % show image on screen  

and after the simle is black out need save it on a second subplot

subplot (212)
imagesc(im_mod); 

Thank you in advance

Answer 1

[Image Analyst]

See my masking and copy and paste demos.

Also check out the Color Thresholder on the Apps tab or the tool ribbon.