Function is not defined – Uncaught ReferenceError

How about removing the onclick attribute and adding an ID:

<input type="image" src="btn.png" alt="" id="img-clck" />

And your script:

$(document).ready(function(){
    function codeAddress() {
        var address = document.getElementById("formatedAddress").value;
        geocoder.geocode( { 'address': address}, function(results, status) {
            if (status == google.maps.GeocoderStatus.OK) {
                map.setCenter(results[0].geometry.location);
            }
        });
    }
    $("#img-clck").click(codeAddress);
});

This way if you need to change the function name or whatever no need to touch the html.