use DCT to add noise

Hi, its a problem with adding noise in my image. i want to add a sin noise with a special freq in both x and y dimensions in my image. my image is 400*400 . but how can i use matlab to create this wave and add it to my image named I? its better to use DCT transforms to make noise...

Answer 1

[Wayne King]

You haven't said anything about the frequency, so I'll just pick one.

 xi=(0:399); yi=(0:399);
 [Xi,Yi]=meshgrid(xi,yi); 
 Z0 = sin(pi/4*Xi) + cos(pi/4*Yi);
 % If Im is your image, the following adds the 2-D sine wave.
 Im = Im+Z0;