Bug 104986 Backgound image uses an absolute path
Currently Chart uses an absolute path to indicate a backgournd image, that may cause the design unusable on other environments. Expected the background image can be definded in multiple ways like in report designer. e.g. URI(absolute path), File(relative path), Embedded Image(Encoded Image Data).
chart/org.eclipse.birt.chart.ui.extension/src/org/eclipse/birt/chart/ui/swt/composites/MarkerIconDialog.java
*            the string to trim
	 * @return the trimmed string, or null if the string is empty
	 */
	private static String trimString( String value )
	{
		if ( value == null )
			return null;
		value = value.trim( );
		if ( value.length( ) == 0 )
			return null;
		return value;
	}
	/**
	 * 
	 * @return If the user clicks "OK", returns true. Otherwise, returns false. 
	 */
	public boolean applyMarkerIcon( )
	{
		return applyMarkerIcon;
	}
	/**
	 * 
	 * @return Returns an icon palette to Line series.
	 */
	public Palette getIconPalette( )
	{
		return iconPalette;
	}
}