<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/06/29/preventing-an-image-from-automatically-loading-in-an-image-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="btn"
                label="Load Image"
                click="img.load();" />
    </mx:ApplicationControlBar>

    <mx:Image id="img"
            autoLoad="false"
            source="assets/Fx.png"
            maintainAspectRatio="true"
            percentWidth="100"
            percentHeight="100" />

</mx:Application>