switch from svg to png fallback working in IE8
overlays are roughly working for dynamic png on at least chrome
now svg shows up with svg-supporting browsers and dynamic png shows up for others
now svg shows up with svg-supporting browsers and dynamic png shows up for others
callbacks added for getting dynamic
PNG
vertical scaling corrected by using single scaling factor for height and for width, based on ratio of png and svg widths
identified stackoverflow as coming from event listener shim added for IE8. removed it, and openseadragon works ok.