You can pull out the part of the image round location (x,y) like this:
pattern = image(y-h:y+h, x-h:x+h);
This assumes that the pattern is a square patch of the image centred on (x,y), and that the size of the pattern is (2*h+1) by (2*h+1).
There are many ways to search for this pattern in this image or in another image, but perhaps the best thing to start with would be normxcorr2, if you have the Image Processing Toolbox. Have a look at doc normxcorr2 and try it out.
