Here's something simple that works - though it's not elegant or efficient:
% image data
bigIm = imread('street1.jpg');
smallysize = 50;
smallxsize = 70;
smallIm = bigIm(188:188+smallysize-1, 177:177+smallxsize-1, :);
% trajectory data
trajy = 400:-5:100;
trajx = trajy;
% animated display
for step = 1:length(trajx)
displayIm = bigIm;
displayIm(trajy(step):trajy(step)+smallysize-1, ...
trajx(step):trajx(step)+smallxsize-1, :) = smallIm;
imshow(displayIm);
pause(0.2);
end
