How can i find the position of a subimage in larger image ?

Hello I have a sub-image X ,which is a subimage of Y .How can find the position of this subiamge in the image Y ? Can anyone help me

Answer 1

[Thorsten]

 F = im2double(imread('cameraman.tif'));
 I = rand(512);
 I([1:size(F,1)] + 30, [1:size(F,2)] + 80) = F;

 disp('Search target using imfilter, this may take some time...')
 If = imfilter(I, F);

 [maxval ind] = max(If(:));
 [y x] = ind2sub(size(If), ind);

 imshow(I)
 hold on
 plot(x, y, 'rx')

Answer 2

[Image Analyst]

Use normxcorr2(). See my demo of it, attached.