How to restrict zooming out of an image displayed

One possible workaround to this would be to use the "ActionPostCallback" callback function for the zoom object corresponding to the UIAxes. Please take a look at the following example which illustrates the workaround. Here, every time the user tries to zoom out beyond the original axes limits, the limits are reset to the original value:

a=uiaxes;
imshow(imread('cameraman.tif'),'Parent',a);
origXLim=a.XLim;
origYLim=a.YLim;
% Listen to zoom events
h = zoom(a);
set(h,'ActionPostCallback',@(x,y)mypostcallback(x,y,origXLim,origYLim));
set(h,'Enable','on');

function mypostcallback(obj,evd,origXLim,origYLim)
    newLim = get(evd.Axes,'XLim');
        if (newLim(2)-newLim(1)) > (origXLim(2)-origXLim(1))
            evd.Axes.XLim=origXLim;
            evd.Axes.YLim=origYLim;
        end
end