Bug 203044 Invoke Script does not work correctly for two similar charts [13]
chart/org.eclipse.birt.chart.device.extension/src/org/eclipse/birt/chart/device/image/JavaxImageIOWriter.java
IIOWriteWarningListener,
		IImageMapEmitter
{
	protected Image _img = null;
	protected Object _oOutputIdentifier = null;
	private Bounds _bo = null;
	private boolean _bImageExternallySpecified = false;
	private static ILogger logger = Logger.getLogger( "org.eclipse.birt.chart.device.extension/image" ); 
	private final static String NO_OP_JAVASCRIPT = "javascript:void(0);"; 
	private final static String POLY_SHAPE = "poly"; 
	
	private Map callbackMethodsRegistry = new HashMap( 5 );
	
	/**
	 * Returns the output format string for this writer.
	 * 
	 * @return
	 */
	protected abstract String getFormat( );